vvEPA
United States
Environmental Protection
Agency
Office of
Solid Waste
and Emergency Response
Superfund
EPA 540/2-86 003 (f)
Office of Emergency
and Remedial Response
Washington DC 20460
September 1986
Mobile Treatment
Technologies
for Superfund Wastes
Hon
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EPA Report No. 540/2-86/003 (f)
September 1986
MOBILE TREATMENT TECHDNOLOGIES
FOR SUPERFUND WASTES
by
Camp Dresser & McRee Inc.
Boston, MA 02108
Versar EPA Contract No. 68-01-7053
CDM Subcontract No. 939-4
Project Officer
Linda D. Galer
Hazardous Response Support Division
Office of Solid Waste and Emergency Response
Office of Emergency and Remedial Response
Washington, D.C. 20460
I1-s: 1 5
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ABSTRACT
The use of mobile technologies to treat wastes at CERCLA-regulated (i.e.,
Superfund) sites is becoming more common. One reason for the increased
focus on mobile systems is the developing concern about the long-term
environmental risks associated vith containment-based methods of waste
disposal. Particularly for large quantities of wastes (e.g., soils),
mobile units may be more practical than shipping wastes off site. A second
reason is that commercial application of many fixed and mobile systems at
RCRA sites is sufficiently developed so that technology transfer to
Superfund sites is possible.
This document addresses the use of established and developing mobile
systems to treat Superfund wastes. The capabilities and limitations of
five broad treatment categories, and specific technologies under each
category, are discussed in the following chapters:
o Chapter 1 Introduction includes background information on mobile
systems, past and present use, future applications, planning
considerations in system use and an overview of document
organization.
o Chapter 2 Thermal Treatment describes the use of various
incineration, pyrolysis and wet oxidation processes as mobile units
to treat Superfund wastes.
o Chapter 3 Immobilization focuses on cement-based or
pozzolan-based fixation processes and discusses their potential use
on Superfund wastes.
o Chapter 4 Chemical Treatment addresses waste treatment via
reduction-oxidation (redox), neutralization, precipitation and
dechlorination.
o Chapter 5 Physical Treatment discusses a wide variety of
processes that physically separate different components of a single
phase or multiple phase waste.
o Chapter 6 Biological Treatment describes the capabilities of
aerobic processes, anaerobic processes, and in situ biodegradation
in treating Superfund wastes on site.
This document was submitted in fulfillment of VERSAR EPA Contract No.
68-01-7053, COM Subcontract No. 939-4, Work Assignment No. 11, by COM,
under the sponsorship of the U.S. Environmental Protection Agency.
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DISCLAIMER
This information has been reviewed in accordance with the U.S.
Environmental Protection Agency's admininstrative review policies and
approved for presentation and publication. Mention of trade names or
commercial products does not constitute endorsement or recommendation for
use.
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ACKNOWLEDGEMENTS
This document was prepared by several individuals at the Boston office of
Camp Dresser and McKee, Inc. The following people have contributed key
chapters of this document.
Bill Glynn (Project Engineer) - Chemical, physical and biological
processes.
Colin Baker (Project Coordinator) - Biological, immobilization
processes.
Tony LoRe - Thermal processes.
Arthur Quaglieri - Immobilization processes.
These people may be contacted for additional information at the following
address:
Camp, Dresser and McKee, Inc.
One Center Plaza
Boston, MA 02108
(617) 742-5151
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TABLE OF CONTENTS
MOBILE TREATMENT TECHNOLOGIES FOR SUPERFUND WASTES
Executive Summary
1.0 Introduction
1.1 Background 1-1
1.2 Past and Present Use 1-2
1.3 Future Use 1-5
1.4 Planning Considerations 1-7
1.5 Document Organization 1-11
2.0 Thermal Treatment
2.1 Introduction 2-1
2.2 Rotary Kiln Incineration 2-7
2.3 Liquid Injection Incineration 2-12
2.4 Fluidized Bed Incineration 2-14
2.5 Infrared Incineration 2-20
2.6 Plasma Arc 2-24
2.7 Advanced Electric Reactor 2-27
2.8 Supercritical Water Oxidation 2-30
2.9 Wet Air Oxidation 2-33
3.0 Immobilization 3-1
4.0 Chemical Treatment
4.1 Introduction 4-1
4.2 Chemical Reduction-Oxidation (REDOX) Treatment 4-2
4.3 Neutralization 4-7
4.4 Precipitation 4-11
4.5 Dechlorination 4-14
5.0 Physical Treatment
5.1 Introduction 5-1
5.2 Air Stripping 5-3
5.3 Mechanical Aeration/Extraction 5-7
5.4 Steam Stripping 5-11
5.5 Distillation 5-14
5.6' Activated Carbon Adsorption 5-17
5.7 Evaporation/Dewatering 5-21
5.8 Soil Flushing/Soil Washing 5-24
5.9 Filtration 5-28
5.10 Ion Exchange 5-30
5.11 Membrane Separation 5-32
5.12 Phase Separation 5-34
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TABLE OF CONTENTS (CONT'D)
6.0 Biological Treatment
6.1 Introduction 6-1
6.2 Aerobic Biodegradation 6-2
6.3 Anaerobic Digestion 6_9
6.4 In situ Biodegradation 6-13
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LIST OF FIGURES
Figure
2.1 Process Flow Diagram of a Mobile Rotary Kiln
Incineration System 2-8
2.2 Process Flow Diagram of Fluidized Bed Incinerator 2-16
2.3 Schematic Diagram of Circulating Bed Incinerator 2-17
2.4 Process Flow Diagram of Infrared Incineration
System 2-21
2.5 Schematic Diagram of Plasma Arc System 2-25
2.6 Schematic Diagram of Huber Advanced Electric Reactor 2-28
2.7 Process Flow Diagram of Supercritical Water Process 2-31
2.8 Process Flow Diagram of Wet Air Oxidation 2-34
4.1 Schematic Diagram of Chemical Reduction of Hexavalent
Chromium (Cr ) 4-3
4.2 Schematic Diagram of Neutralization 4-8
4.3 Schematic Diagram of Chemical Precipitation and
Associated Process Steps 4-12
4.4 Block Diagram of Dechlorination Slurry Process 4-15
5.1 Packed Column Air Stripper: Design Basis, Side,
Top, and On Road Views 5-4
5.2 Schematic Diagram of Low Temperature Thermal Stripper 5-8
5.3 Schematic Diagram of Steam Stripper 5-12
5.4 Schematic Diagram of Batch and Continuous Distillation 5-15
5.5 Schematic Diagram of Granular Activated Carbon Columns 5-18
5.6 Schematic Diagram of Single and Multiple Effect
Evaporators 5-22
5.7 Schematic Diagram of Recycle Flow Dissolved Air
Flotation System 5-35
6.1 Schematic Diagram of Activated Sludge Biological
Treatment 6-3
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LIST OF FIGURES (CONT'D)
Figure
6.2 Schematic Diagram of Rotating Biological Contractor 6-4
6.3 Schematic Diagram of Conventional and High Rate
Anaerobic Digesters 6-10
6.4 Schematic Diagram of In Situ Biodegradation 6-14
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LIST OF TABLES
Table
1.1 Partial List of Alternative Treatment'Methods Used
to Manage CERCLA Wastes 1-3
1.2 Mobile Technology Description: Format Summary 1-12
1.3 Suitability Screen of Potential Mobile Technologies 1-13
1.4 Summary Data on Mobile Technologies 1-15
2.1 Mobile Thermal Treatment Systems 2-3
3.1 Mobile Immobilization Systems 3-5
6.1 Mobile Biological Treatment Systems 6-7
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EXECUTIVE SUMMARY
Mobile treatment technologies have many applications to the treatment of
wastes at many sites governed by the Comprehensive Environmental Response
Compensation and Liability Act (CERCLA) or Superfund. This document
focuses on use of both established and developing mobile systems to treat
Superfund wastes. The goal of presenting this information is to guide
policy planners, on-scene coordinators and remedial project managers in
implementing mobile treatment systems to clean up abandoned hazardous waste
sites.
This report has been designed to provide information on the status of
mobile treatment and the application of mobile treatment systems at
Superfund sites. Both the public and policymakers are becoming more aware
of the long-term environmental risks associated with using a
containment-based strategy (e.g., landfills, site capping) to dispose of
Superfund waste. Hence, there is a greater emphasis on the use of
alternative technologies at Superfund sites.
Utilization of mobile treatment systems requires an understanding of the
capabilities and limitations of these systems. Important technology
information includes the following:
o Technical basis of the process,
o Types of waste a unit can handle,
o Restrictive waste characteristics,
o Requirements for use on site,
o Potential environmental impacts,
o Cost, and
o Commercial availability.
This document presents an overview of technologies currently available for
use as mobile systems and technologies that have potential application to
treatment of wastes on Superfund sites. Each section addresses a general
treatment category and describes available and developing technologies
within that category. Each of the topics listed above is discussed.
The information on technologies represents a synthesis of background
technical information and information supplied by vendors. Detailed
information supplied by vendors on particular mobile systems is compiled in
a supplemental document, Superfund Treatment Technologies: A Vendor
Inventory (EPA, 1986).
New developments are occurring rapidly in the field of mobile treatment
systems. For additional, up-to-date information contact:
o EPA Office of Research and Development
Hazardous Waste Engineering Research Laboratory
26 W. St. Clair
Cincinati, Ohio 45268
o Individual vendors of specific systems listed in the appendix and
the Vendor Inventory.
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1.0 INTRODUCTION
1.1 BACKGROUND
Mobile waste processing systems are presently employed to treat some
hazardous wastes regulated under the Resource Conservation and Recovery Act
(RCRA). Mobile treatment systems also have application to the treatment of
wastes subject to the Comprehensive Emergency Response and Liability Act
(CERCLA), often called Superfund. The opportunity for technology transfer
(from RCRA to CERCLA) and the increased need for mobile systems to treat
Superfund wastes is the focus of this document.
Mobile treatment systems usually consist of modular equipment that can be
brought onto a site (e.g., by truck or railcar) and can be transported to a
number of different sites over the life of the equipment. Size and
configuration of the equipment may differ considerably from the
conventional equipment used in permanent structures. In general, the
equipment is smaller than conventional equipment in order to allow
over-the-road mobility. However, one large piece of equipment may be in
several parts on separate trucks, trailers or railcars. The equipment may
also consist of several removable components in order to accommodate the
needs of different sites. Mobile treatment systems may be skid-mounted,
prepiped and prewired for fast response to emergency situations or they may
require assembly on site before operations commence and disassembly prior
to transporting to another site. Because some systems require assembly and
auxiliary equipment on site, mobile treatment systems are often referred to
as "transportable", instead of "mobile."
Mobile systems show considerable promise for remedial activities at
Superfund sites. These technologies can provide a permanent solution with
many advantages over alternatives involving offsite transport and disposal.
While the experience base is somewhat limited, interest in mobile systems
is rapidly growing. The number of vendors offering viable systems has
increased dramatically in recent years.
This document presents a review of treatment technologies that may be used
as mobile systems and discusses those technologies that vendors are
developing for use as mobile systems in the next few years. Waste
characteristics, environmental impacts, costs (if available) and other
development and implementation factors were considered in assessing the
potential role of these mobile systems.
Specific information on the capabilities of numerous mobile systems have
been supplied by vendors. This information has been compiled, and is
available for reference (Superfund Treatment Technologies: A Vendor
Inventory (EPA, 1986)). The Vendor Inventory contains vendor-supplied
summaries of mobile unit capacity, availability, and performance, as well
as limited cost data. These companies are listed in the technology
reviews provided in this document, and contacts are listed from whom
further information can be obtained. The companies are also listed in the
Appendix to this document.
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1.2 PAST AND PRESENT USE
The concept of using mobile treatment systems to process water and wastes
is fairly well-established. The United States military has developed and
used mobile water treatment units for providing potable water and for
treating sewage. Additionally, many conventional wastewater treatment
systems have been modularized to the extent that small-scale systems can be
practically considered transportable (e.g., equipment on oil rigs, ships,
and airplanes).
The application of the mobile concept to uncontrolled hazardous waste sites
is also not new. Under EPA sponsorship, mobile equipment has been
developed for emergency response and used to contain, collect, and in some
cases, provide preliminary treatment of accidentally released hazardous
materials and contaminated groundwater. The types of mobile equipment that
have been developed by the EPA for emergency response include:
o A carbon adsorption/sand filter system,
o A rotary kiln incineration system,
o An in situ containment/treatment unit (ISCTU),
o A soil washer system,
o An activated carbon regeneration system,
o A flocculation-sedimentation system,
o A reverse osmosis (RO) treatment system, and
o An independent physical/chemical (IPC) wastewater treatment system.
Some of the systems listed above are not fully developed or have not yet
been field-tested. Some of the systems and their status are discussed
later in the appropriate section.
Experience with use of mobile systems at Superfund sites is limited but the
concept has been or is being incorporated for both remedial response and
waste removal. Some past, planned, and ongoing activities involving mobile
systems at uncontrolled hazardous wastes sites are described in Table 1.1.
In spite of the increased use of mobile treatment systems for both
emergency responses and remedial actions at hazardous waste sites, many
factors have contributed to the limited application of mobile systems at
Superfund sites. These factors include:
o Lack of knowledge concerning mobile units,
o Ready availability of land disposal alternatives,
o Generally higher costs and longer periods for development and
operation for alternative technologies,
o Developmental nature of some technologies,
o Local institutional issues of concern, and
o Limitations of capacity, materials handling or process
characteristics which prevent the mobile concept from being a
"total solution."
The restrictive characteristics of specific mobile technologies are
discussed in subsequent sections of this document.
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TABLE 1.1
PARTIAL LIST OF ALTERNATIVE TREATMENT METHODS USED
TO MANAGE CERCLA HAZARDOUS WASTES
Site
Status
Bridgeport, NJ Completed
(remedial)
Bruin Lagoon, PA
Florida Steel
Completed
(remedial)
Demonstration
completed
Waste Type
Aqueous waste containing
volatile organics
Acid asphaltic sludges
Soil containing PCBs
Treatment Technology
Phase separation, air
stripping, carbon
adsorption* sludge
devatering
2
Immobilization
Thermal destruction
by pilot-scale infrared
thermal unit
General Refining, Ongoing
GA (removal)
Kent, WA
Lee's Farm, WI
Ongoing
Ongoing
Sludge containing
sulfuric acid, oil,
metals; filter cake
containing organics,
metals
Waste oil containing
dioxins
Soils containing lead
Solvent extraction
of organics
Chemical destruction/
precipitation of
dioxins using K/PEG
(potassium/polyethylene
glycol)
Soil-washing to remove
Love Canal, NY
McKin, NH
Preparation of
demonstration
Demonstration
completed
Leachate containing
dioxins
Sandy soils containing
volatile organics
Thermal destruction
by plasma arc unit
Enclosed thermal soil
aeration followed by
carbon adsorption of
gases and cement
immobilization of
treated soils
1. Status as of August 1986
2. On-site, mobile unit
3. On-site, stationary unit
A. Off-site unit, potentially mobile
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TABLE 1.1 (CONT'D)
PARTIAL LIST OF ALTERNATIVE TREATMENT METHODS USED
TO MANAGE CERCLA HAZARDOUS WASTES
Site
Montana Pole, MT
Outboard Marine
Corp., IL
Peak Oil, FL
Status
Completed
(removal)
Demonstration
completed
Demonstration
completed
Waste Type
Diesel fuel (recovered
from groundwater)
containing pentachloro-
phenols (PCPs) and
dioxins
Sediments containing
PCBs
Soil containing PCBs
Treatment Technology
Chemical destruction/
precipitation of PCBs,
dioxins using K/PEG
(potassium/polyethylene
glycol)
Low-temperature gas
extraction of organics
Thermal destruction by
pilot-scale infrared
thermal unit
Peak Oil, FL
Negotiations
in progress
Soil containing PCBs
Thermal destruction by
pilot-scale infrared
thermal unit
Sylvester, NH
Tibbett's Road,
NH
Ongoing
Preparation
for removal
Groundwater containing
organic and metals
Soil containing dioxins
Precipitation followed
by air stripping and
incineration of
emissions; tertiary
biological treatment
for discharge to stream;
sludge dewatering and
encapuslation
Thermal destruction by
pilot-scale infrared
thermal unit
Times Beach, MO
Demonstration
completed
Soil containing dioxins
Thermal destruction by
pilot-scale infrared
thermal unit
Western
Processing, WA
Completed
Oil containing dioxin
(120 ppb)
Thermal destruction by
pilot-scale infrared
thermal unit
Verona Well
Field, MI
Ongoing
Groundwater containing
volatile organics
Air stripping followed
by carbon adsorption
air emissions
2. On-site, mobile unit
3. On-site, stationary unit
4. Off-site unit, potentially mobile
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1.3 FUTURE USE
Land disposal of hazardous waste is becoming less acceptable as a means of
managing uncontrolled hazardous waste sites. Congress, EPA and the public
are realizing that land disposal does not offer a final solution to the
hazardous waste problem rather than providing a method of treatment,
land disposal often provides only temporary containment. As a result, many
wastes will be restricted from land disposal within the next five years.
Developing alternatives to land disposal is therefore imperative.
Readily available mobile onsite treatment may be preferable to treatment at
offsite stationary facilities because of the elimination of high
transportation costs for large quantities of waste. Stationary commercial
facilities may not have adequate capacity for these wastes. Also, risks to
public health and the environment may be decreased for a site response
because hazardous materials are not transported off site. As wastes are
treated on site rather than moved to other locations, the problem is
resolved at the source.
The number of mobile systems available or under development has increased
substantially in the past year (see Superfund Treatment Technologies; A
Vendor Inventory, EPA, 1986). The availability of mobile systems should
continue to increase rapidly over the next few years, based on the number
of vendors who have expressed interest in developing mobile systems to meet
the needs of Superfund.
A lack of data pertaining to mobile treatment systems is limiting the use
of these methods. As more systems are developed and used, information on
their cost and reliability will continually improve. The availability of
these data will further stimulate mobile treatment use.
There are a number of impediments to development and commercial use of
mobile treatment systems as well as fixed alternative treatment methods.
Some of these impediments are listed below:
o Substantial delays and cost increases resulting from complicated
procedures for environmental permitting,
o The shortage of reliable and comparable technical performance
information and standardized cost data,
o Uncertainties in scale-up of designs from bench- or pilot-scale,
o Uncertainty in the performance and treatment standards for many
pollutants,
o Difficulty in obtaining liability insurance to cover operational
risks during development and testing of various technologies,
o Potentially responsible party (PRP) concerns about liability in the
event of innovative technology failure,
o Hesitation by states to use innovative technologies given the
perceived uncertain reliability of such technologies, and
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o Tendency of concerned communities surrounding Superfund sites to
prefer remedial alternatives that remove all hazardous substances to
a management facility that is far from the site. Innovative onsite
technologies may, therefore, appear less attractive from the
adjacent community's point of view.
In spite of these impediments, options are being considered, and in some
cases, used to remove impediments or create incentives to promote
development of innovative mobile technologies.
For example, amendments to CERCLA now pending may solve the potentially
response party (PRP) concerns about liability by allowing EPA to indemnify
those participating in cleanups. In addition, state support for mobile
systems is increasing. Illinois has requested bids for mobile incineration
systems. New York currently owns a pyrolysis (plasma arc) system and will
be testing it soon at Love Canal.
Many fixed technologies are currently available and are used by a number of
large industries for RCRA wastes. Modifications of these units (i.e.,
smaller sizes and modular construction) to accommodate mobility could
probably be accomplished in a relatively short time (less than six months).
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1.4 PLANNING CONSIDERATIONS
Mobile treatment systems can be designed and operated to handle almost any
waste type processed by permanent units. However, the limited experience
in the use of these systems necessitates a very close assessment of their
applicability, design, and operation on a case-by-case basis.
There are many planning considerations which must be incorporated into an
assessment of the viability of mobile systems for a particular site. The
direction provided in EPA guidance documents on planning remedial
investigations and feasibility studies is very useful in this assessment.
Some of the more critical planning considerations are:
o Waste characteristics,
o Site constraints,
o Potential environmental impacts,
o Costs, and
o Technology support requirements.
Each of these factors is addressed below.
It is important to note that the type and quality of data needed to make
assessments of the feasibility of utilizing a particular mobile treatment
system often are not available from the initial remedial investigation.
Generally, the initial data on site contamination was collected for the
purposes of assessing the health risk to the local population. These data
are not usually sufficient to assess waste treatability. Therefore, the
data required to assess treatability should be considered when determining
data collection objectives for the remedial investigation.
This extra effort and expense can be reduced if initial data collection
objectives and treatability data requirements are considered during the
planning stages of a remedial investigation/feasibility study.
Waste Characteristics
It is important to identify and assess both favorable and restrictive
characteristics of wastes with respect to each treatment system. Examples
of characteristics to consider in selecting a treatment system are:
o Waste variability and requirements for treatment performance. Some
technologies can handle a wide range of waste characteristics with
consistent treatment performance while others are more susceptible
to variable waste conditions.
o Non-toxic waste components. Operational problems such as fouling
and plugging of equipment can result from otherwise innocuous
components such as iron, suspended solids, and naturally occurring
organic material.
o Need for pretreatment. Some wastes may require a more elaborate
treatment process while others may be treated by a less capital
intensive treatment process such as fixation/solidification.
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Each mobile technology review presented in the following chapters
identifies the waste types that can be processed with that unit.
Restrictive waste characteristics, (i.e., waste types or forms that may
interfere with efficient operation) are identified. Requirements for both
pretreatment and post treatment are discussed.
Site Preparation
Manufactors need to be considered in evaluating the appropriateness and
implementability of onsite treatment. These factors are listed below.
o Impact on the local community,
o Protection of the equipment from vandalism or theft,
o Existence of adequate electric utilities, water supply and
sewer lines,
o Roads for large trailer accessibility,
o Slope stability of the land,
o Soil conditions,
o Location of flood plains, and
o Local zoning ordinances.
Mobile treatment systems should rely as much as possible on existing
utilities in order to speed up implementation and to prevent unnecessary
capital expenditures on auxiliary equipment. Site preparation required to
operate a mobile system may include:
o Access roads,
o Concrete pads for equipment,
o Accidential spill control and staging, and
o Connections to public utilities.
Potential environmental impacts, reviewed in the next section, must also be
weighed in the equipment siting decision.
Potential Environmental Impacts
Environmental impacts are an important consideration with regard to mobile
systems. As stated earlier, mobile systems offer several advantages over
offsite stationary facilities, such as eliminating waste removal and
transportation risks. The advantages over containment technologies has
also been noted. However, onsite remediation activities may pose risks to
the surrounding population and local environment. Federal, state and local
regulations for environmental protection must always be carefully
considered for their applicability to the action being evaluated. The way
in which such requirements are implemented is particularly important in
obtaining community support for more innovative alternatives, such as
mobile treatment.
Air pollution can be a major concern for incineration systems and air
stripping systems. Hazardous constituents must be identified and their
transport away from the facility anticipated under worst-case situations
(e.g., stagnant air and thermal inversions).
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Road construction and intensive activity on site may create additional
pollution problems such as airborne particulate dust, surface runoff and
erosion. These emissions of fugitive dust are of particular concern if
disturbed soils are contaminated.
Noise generated during waste treatment or during equipment transport may be
disturbing to nearby residents.
State and local regulatory authorities and local citizens groups will often
expect full evaluations of environmental impacts to air, water and the
local environment.
Every effort should be made to minimize these impacts by selecting the
proper location for the mobile units and by following good engineering
practices. Health and safety of workers and nearby residents must be
considered and sufficient precautions should be incorporated into the
remedial program design.
Residuals generated by the selected treatment process must be handled in an
environmentally safe manner in order to minimize potential impacts.
Concentration and quantity of residuals must be assessed early in the
selection process so that proper treatment and/or disposal can be
incorporated into the overall process. Extensive requirements or
restrictions with respect to residuals for one treatment process may make
the use of other treatment technologies more favorable. Adequate
allowances of time should be made for a thorough evaluation of regulatory
requirements.
Costs
The cost of implementing mobile treatment technologies is also important in
determining the preferred alternative. There are some major cost concerns
which may affect the selection of one technology over another.
First, with all alternatives, capital, operating and maintenance costs must
be carefully reviewed to assess the economic impacts to the remedial
program.
In addition, many mobile units have not been previously utilized at
Superfund sites. Some units may have been used to treat only
RCRA-regulated waste. Therefore cost information, if available, may be for
site conditions or waste stream characteristics that are much less variable
than those found at Superfund sites. Waste-specific characteristics can
greatly affect the costs of a remedial program and efforts to provide
detailed cost estimates for these technologies must usually be made on a
case-by-case basis.
Technology Support Requirements
The use of specific mobile treatment systems should include an assessment
of support requirements, including the following:
o The utilities required (e.g., electricity, water, wastewater, fuel,
cooling) for system operation;
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The availability of utilities at the site and the services required
for the treatment system (e.g., laboratory, maintenance); and
The extent of training required for the operating labor force. In
general, the labor force for a mobile treatment system used at a
Superfund site will require more training because the monitoring
requirements for the process operation will be more intensive than
for permanent treatment systems or for non-process alternatives.
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1.5 DOCUMENT ORGANIZATION
Format Summary
The material presented in this document is structured to provide project
planners, on-scene coordinators (OSCs) and remedial project managers (RPMs)
with information on the applicability and capabilities of mobile treatment
as an alternative to land disposal of contaminated materials. A uniform
format was developed for the presentation of the alternative mobile
technology review presented in subsequent sections of this document. This
format is summarized in Table 1.2.
The level of detail provided for each mobile technology review depends on
the state of development and availability of information. While the
principal focus has been on mobile systems that have a more proven
"track record", other developing mobile technologies have been included as
appropriate. Because all technologies discussed are not at the same stage
of development, the text presentation on some methods may vary from the
format summarized in Table 1.2.
Overview of Technology Selection
A technology matrix (Table 1.3) is included in this section to provide a
cross reference for matching potentially applicable mobile technologies
with general waste types. This matrix is only a guide for general
technology applications and should not be used to specify a particular
treatment technology for a specific waste stream or material without
extensive review of that application.
The inclusion of the mobile treatment technologies discussed in the
following chapters was based on the extent of application of each
particular technology to RCRA and CERCLA wastes. If the data are limited
on CERCLA waste applications, then application on RCRA wastes was reviewed
to determine the feasibility of treating similar CERCLA wastes.
Limitations in Technology Selection and Transfer
There are some important differences and limitations in transferring
technologies from RCRA to CERCLA wastes, although both waste types can be a
mixture of contaminants. The specific limitations associated with
technology selection for CERCLA waste treatment are summarized in the
following paragraphs.
Wastes that are mixed in composition and/or contaminant concentration are
more difficult to treat because one specific technology may not be suitable
for all waste types and concentrations contained within the mixture.
Several technologies applicable to uniform RCRA wastes are very sensitive
to changes in the feed composition and concentration, which can reduce
effective contaminant removal. Thus, CERCLA wastes which are highly
variable must be processed carefully.
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TABLE 1.2
MOBILE TECHNOLOGY DESCRIPTION:
FORMAT SUMMARY
Process Description;
One to two paragraph description to include process diagram, status
(full-scale versus pilot-scale), normal operating conditions, and
auxiliary controls.
Waste Type Handled:
Wastes processed by this system (e.g., sludge, soil, air, water,
contaminated with phenolics, metals) and other waste characteristics
(e.g., pH, concentration).
Restrictive Waste Characteristics;
Waste types not suitable for treatment, characteristics of waste (with
concentrations) that may be incompatible with treatment method.
Required Onsite Facilities/Capabilities;
Size and configuration of units, site preparation, labor force,
utilities (e.g., electricity, water, fuel, cooling) and services (e.g.,
lab, maintenance facilities).
Environmental Impacts;
Air pollution considerations, residuals treatment or disposal, road
construction., health and safety.
Costs (if available):
Capital costs of typical units, operation and maintenance costs (e.g.,
electricity, fuel).
Commercial Applications;
Vendors with commercially available systems or units under development.
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TABLE 1.3
SUITRBILITV SCREEN OF POTENTIRL rtOBILE TECHNOLOGIES
Technology
Q>
CO
Aqueous Wastes:
Metals
Highly Toxic
Organics
Volatile
Organics
Toxic Organics
Radioactive
Corrosive
Cyanide
Pesticide
Asbestos
Explosive
uj. Organic Liquids:
§[ Metals
Highly Toxic
Organics
Volatile
Organics
Toxic Organics
Radioactive
Corrosive
Cyanide
Pesticide
Sludges/Soils:
Metals
Highly Toxic
Organics
Volatile
Organics
Toxic Organics
Radioactive
Corrosive
Cyanide
Pesticide
Asbestos
Explosive
0)
00
3:
Incineration
x
O
O
o
x
x
O
o
x
O
o
o
x
*
x
X
X
O
X
0
Pyrolysis
x
O
0
o
x
x
O
o
x
x
O
x
x
*
O
x
X
O
X
O
Wet Oxidation
x
X
X
X
X
X
X
X
X
X
X
0
X
X
Neutralization
O
O
O
x
O
O
x
x
X
X
X
X
X
O
X
X
X
X
X
X
X
o
Precipitation
O
O
O
o
o
o
x
x
x
O
o
x
x
X
X
0
X
X
O
X
X
Distillation
Air Stripping/
Soil Aeration
x
X
O
X
X
X
X
0
X
X
O
0
x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Activated
Carbon
O
x
X
X
X
X
O
X
X
X
X
X
X
o
O
X
X
X
X
Evaporation/
Dewatering
x
X
X
X
X
X
X
X
X
o
X
X
X
X
X
X
X
X
Phase
Separation
x
X
X
X
X
O
0
O
0
o
o
o
x
0
x
x
O
x
Fixation
Extraction/So
Washing
Membrane Sep.
Ion Exchange
X
X
X
X
X
X
X
X
X
X
o
X
X
X
o
X
X
X
o
O
O
0
0
o
x
x
x
O
x
O
x
X
X
X
X
X
X
X
0
O
O
X
X
X
X
O
0
X
X
X
O
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Evaporation
X
O
X
X
O
X
X
X
O
X
X
X
O
X
O
X
X
X
X
X
Filtration
x
X
X
X
X
X
X
X
o
X
X
X
X
X
O
X
X
X
O
X
X
Activated Slut
x
O
O
x
x
O
0
x
0
x
x
x
x
x
x
X
X
X
X
X
X
X
X
X
X
X
X
In situ
Biodegradatiol
x
O
O
x
x
x
x
x
O
x
X
X
X
X
X
X
X
X
o
0
X
X
O
O
x
O
Applicable O Potentially Applicable x Not Applicable
1-13
-------
The variability in CERCLA wastes may be a result of a number of factors,
including:
o The synergistic reactions that occur between codisposed waste types
or between wastes and naturally occurring organic compounds. The
result of these interactions may be changes in physical and chemical
properties that significantly affect treatment removal efficiencies.
Certain contaminants or naturally occurring organics (e.g., humic
substances and fulvic acid compounds) may interfere with the
separation and/or dilution process for the contaminants of concern.
These synergistic effects are not well understood.
o The natural processes that occur over time such as waste percolation
through soils, distribution and transport due to rain. These
processes may result in varying contaminant concentration vertically
and/or laterally within a Superfund site which makes waste
extraction and treatment more difficult.
In summary, transfer of treatment technologies from RCRA wastes to CERCLA
wastes is complicated by the variable nature of CERCLA wastes. Therefore,
use of a mobile treatment technology at a particular Superfund site may
require extensive laboratory and/or pilot scale treatability studies to
assess the specific application of a treatment technology to wastes of a
particular composition.
Technology Summary
A summary table of the mobile treatment technologies (Table 1.4) is
included to provide an overview for comparison of the particular
technologies. More information on each mobile treatment technology is
detailed in the following sections.
1-14
-------
TABLE 1.4
SUMMARY DRIA OH MOBILE TECHNOLOGIES
I
I>
Ul
Primary Waste
Mobile Types Treated
TECHNOLOGY
Unit
Status Class
THERMAL TREATMENT
Incineration
Rotary Kiln
Liquid Injection
Fluidized Bed/
Circulating Bed
Infrared
Pyrolysis
Plasma Arc
Advanced Elec. Reactor
"Wet Oxidation"
Supercritical Water
Oxidation
Wet Air Oxidation
IMMOBILIZATION
Fixation/Solidification
Cement based
Flyash or Lime based
Asphalt-based
REMOVAL TECHNOLOGIES
Chemical
Oxidation-Reduction
Neutralization
Precipitation
Dechlorination
Physical
Distillation
Steam Stripping
Phase Separation
Air Stripping
Activated Carbon
Clarification
Evaporation
Soil Washing
Filtration
Ion Exchange
Membrane Separation
Biological Treatment
Aerobic
Anaerobic
Commercial
Commercial
Pilot
Pilot
Pilot
Pilot
Pilot
Commercial
Commercial
Commercial
Pilot
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Pilot
Commercial
Commercial
Pilot
Commercial
Comae rcial
0
O
o
0
0
0
O
0
I
I
I
1,0
I,O
I
o
o
0
0,1
o
o
I
0,1
0,1
I
I
0,1
0
o
Form
S,L
L
S,L
S,L
L
S,L
L,GW
L
S
S
dry S
S,L,GW
S,L,GW
L,GW
L,S
L,GW
S,L,GW
S, L
GW,S
GW
GW,L
L,S
S
GW,L,S
GW
GW,L
GW,L
GW,L,S
Immobilization/
Removal/ Air
Destruction
Capability
Very High
Very High
Very High
Very High
Very High
Very High
Very High
High
High
High
High
Moderate
High
Moderate
High
High
High
Moderate
High
Very High
Moderate
High
Moderate
High
Very High
Very High
High
High
Decrease in or
Further
Emissions Treatment/
Relative
Estimated costs
Residues Management
Waste Volume Generated
High
High
High
High
High
High
High
Moderate
Increase
Increase
Increase
Moderate
Moderate
High
High
High
High
Moderate
High
High
Moderate
High
High
High
High
High
Moderate
Moderate
A,L,S
A,L,S
A,L,S
A,L,S
A,L
A,L,S
A,L,S
L
A
A
A
A,S
A,S
S
L,S
L
L
L,S
A,L
L
L,S
L,S
L,S
L,S
L
L
L,S
L,S
Required
Inorganics in ash/landfill
Inorganics in ash/landfill
Inorganics in ash/landfill
Inorganics in ash/landfill
Inorganics in ash/landfill
Inorganics in ash/landfill
Capital
High
High
High
High
High
High
Inorganics in treated stream High
Inorganics/organics in
Landfill
Landfill
Landfill
Dewatering/Landfill
Dewatering/Landfill
Dewatering/Landfill
Landfill
Recycle/dest ruction
Recycle/destruction
Landfill/destruction
Treatment of air emissions
Carbon Regeneration
Landfill
Landfill/destruction
Washing Fluid Treatment
Dewater/landfill
Recycle/destruction
Recycle/destruction
High
Low
Low
Medium
Low
Low
Low
Medium
High
High
Moderate
Low
High
Low
Low
Moderate
Low
High
High
OSM
High
High
High
High
High
High
High
High
Low
Low
Medium
Medium
Medium
Medium
High
High
High
Low
Low
High
Low
High
Moderate
Moderate
Moderate
High
Dewatering sludge/landfill/
destruction
Dewatering sludge/landfill
Low
Low
Low
Low
Emissions or Residues
Mobile Unit Status
Waste Class
Commercial = Full Scale/Operational
Pilot = Demonstration Scale/Operational
0 = Organic
I = Inorganic
Waste Fora
S = Solids/Sludge
L = Concentrated Liquid
GW = Groundwater
(low concentration)
Removal Efficiency Generated Byproduct
Very High - >99% A =
High - 95% L =
Moderate - 90% S =
Air
Liquid, concentrated
Solid
-------
-------
2.0 THERMAL TREATMENT
2.1 INTRODUCTION
Thermal treatment is a term associated with the use of high temperatures as
the principle means of destroying or detoxifying hazardous wastes. There
are several thermal processing methods, some''of which are well-developed
and proven, others that are in the development stage. The three major
thermal processing modes with mobile applications are:
o Incineration,
o Pyrolysis, and
o Wet oxidation.
These thermal treatment methods are summarized here. More specific
information on their applications is given in the sections that follow.
Low temperature thermal volatilization (i.e., stripping) is discussed in
Section 5.3.
Incineration involves the controlled combustion of organic wastes under net
oxidizing conditions (i.e., the final oxygen concentration is greater than
zero) and encompasses most of the well-developed thermal technologies. In
pyrolysis, thermal decomposition occurs when wastes are heated in an oxygen
deficient atmosphere. The process conditions range from pure heating
(thermolysis) to conditions where only slightly less than the theoretical
(stoichiometric) air quantity is supplied. Gases are the principle product
generated by the pyrolytic reaction although ash can also be generated.
Wet oxidation is a thermal processing mode in which organic materials are
broken down through the use of elevated temperatures and pressures in a
water solution or suspension. The processes that utilize the basic
principles of wet oxidation and have been applied to hazardous waste
treatment are supercritical water oxidation and wet air oxidation.
The incineration, pyrolytic, and wet oxidation processes used to treat
hazardous wastes that currently have the best potential for mobile
applications are listed below. The later sections that discuss these
processes are given in parentheses.
o Incineration
- Rotary Kiln (Section 2.2)
- Liquid Injection (Section 2.3)
- Fluidized Bed (Section 2.4)
- Infrared (Section 2.5)
o Pyrolysis
Plasma Arc (Section 2.6)
- Advanced Electric Reactor (AER) (Section 2.7)
o Wet Oxidation
- Supercritical Water Oxidation (Section 2.8)
- Wet Air Oxidation (Section 2.9)
2-1
-------
Table 2.1 lists companies offering these proceses as mobile systems.
Though other firms are developing mobile systems, only those companies with
an operating mobile unit are listed. GA Technologies Inc. is included
since it is the only firm developing a mobile circulating fluidized bed.
Additional information is provided in the appropriate section under
commercial applications.
Thermal treatment in fixed facilities is frequently used to treat hazardous
wastes. The advantages of thermal treatment include:
o Volume reduction,
o Detoxification,
o Energy recovery, and
o Materials recovery.
Thermal treatment offers essentially complete destruction of the original
organic waste. Destruction and removal efficiency (ORE) achieved for waste
streams incinerated in a properly operated thermal processes often exceed
the 99.99 percent required by RCRA for most hazardous wastes. Hydrogen
chloride (HC1) emissions are also easily controlled. Furthermore,
available air pollution control technologies can effectively address the
potential for particulate emissions.
The following sections discuss the general characteristics of mobile
thermal treatment systems and outline existing thermal treatment
technologies and their applications as mobile systems. Due to the nature
of hazardous waste treatment, modifications to these basic technologies are
continually developed. The information presented here gives the status of
existing hazardous, waste thermal treatment processes as documented in
current literature and may change as existing systems improve and new
systems are developed.
Required Onsite Facilities/Capabilities
Because the required site preparation, equipment and utilities are similar
between thermal systems, a general discussion of these elements is provided
here rather than repeating the information for each thermal process.
Despite the fact that the basic technologies are the same as those used in
fixed facilities, there are several factors that need to be considered when
utilizing a thermal technology as a mobile or transportable system.
General considerations associated with mobile systems include:
o Method of transport,
o Ancillary support equipment,
o Utilities,
o' Site preparation,
o Mobilization/demobilization, and
o Residuals/effluents.
These factors are discussed in more detail below.
Method of Transport. The method of transport for thermal technologies
depends on the size and configuration of the mobile unit. For ease of
2-2
-------
TAKE 2.1
HJfllE TflHWAL TRMMNT SYSTHS
i
GO
DEKSDO
Thermal Technology
Rotary kiln
Waste Types Handled
Mobile System Status
EN5CO EnviromiEntal Services Rotary kiln
GA Technologies Inc.
J.M. Huber Corporation
Modar Inc.
Circulating
fluidized bed
Advanced electric
reactor
Supercritical
water oxidation
Shirco Infrared Systems Inc. Infrared
incineration
Waste-Tech Services Inc. Fluidized bed
Westinghouse Plasma Systems Plasma arc
Winston Technology
Zimpro Inc.
Rotary kiln
Wet air oxidation
Combustible wastes; soils Demonstration-scale
contaminated with combustibles system operating.
Organic-contaminated solids, Full-scale systems
liquids, sludges, soil; operating
organics include PCBs, dioxins
Organic-contaminated solids,
liquids, sludges, soil
Organic-contaminated solids,
liquids, soil; organics in-
clude PCBs, dioxins, chemical
warfare agents
Organic-contaminated liquids
Mobile system
under design
Pilot-scale system
operating
Pilot-scale system
operating
Organic-contaminated solids,
sludges, soil; organics in-
clude PCBs, dioxins; explosives
Organic-contaminated solids,
liquids, sludges, soil
Organic-contaminated liquids
Organic-contaminated solids,
liquids, sludge, soil; organ-
ics include PCBs
Organic-contaminated liquids,
sludges
Pilot-scale
system operating
Demonstration-scale
system operating
Pilot-scale system
constructed
Full-scale systems
constructed
(awaiting trial burn)
Full-scale systems
operating
Capacity
3000 Ib/hr soils
35 MM Btu/hr
solids to rotary kiln
10,000 Ib/hr, liquids
to rotary kiln 3,000
Ib/hr, liquids to sec.
comb. 4,000 Ib/hr.
9 MM Btu/hr
10,000 Ib/hr soil
600 Ib/hr hydrocarbons
3000 Ib/hr
30 gal/day of organic
material in an aqueous
waste containing 1-100%
organics
100 Ib/hr
Not available
60 gal/hr
Mi Btu/hr
600 gal/hr
-------
transport, thermal units are generally designed to allow permit-free
hauling (i.e., meet federal and state weight and size restrictions) over
interstate highways via 45-foot long tractor trailers. Many pilot-and
demonstration-scale systems are contained on one tractor trailer.
Full-scale systems are generally mounted on multiple flat bed trailers.
Each trailer typically contains a major system component designed to be
interconnected. Depending upon the site location, other modes of
transportation such as rail or barge may also be considered.
Ancillary Support Equipment. Ancillary support equipment will depend
largely on the site and waste streams. Equipment that may be required for
onsite thermal treatment includes:
o Bulk fuel storage tanks,
o Waste storage, holding and blending tanks,
o Liquid transfer and feed pumps,
o Process water tanks,
o Ash receiving drums,
o Solids handling, preparation (if required) and feed equipment,
o Analytical laboratory support,
o Personnel and maintenance facilities,
o Wastewater treatment facilities, and
o Residue disposal equipment.
Utilities. The principle utilities that may be required for onsite thermal
treatment include:
o Process water,
o Electrical power,
o Steam, and
o Auxiliary fuel.
Because of the remote location of many sites, electrical power may not be
available. In that event, mobile systems can generally be equipped with
diesel generators for electrical power. Most mobile systems that require
steam utilize waste heat boilers to produce the steam on site. Process
water, if not available on site from wells or surface water, must be piped
on site or brought on site in tankers.
Site Preparation. Other site requirements for implementing a mobile
thermal system include:
o Availability of an access road, particularly in remote locations;
o Graded, graveled area to set up the complete system;
o Concrete base or pads for certain system components (e.g., rotary
kiln);
o Spill control/containment measures; and
o Fencing to protect the site area from intruders and inadvertant
contact.
Many of these requirements also apply to other mobile technologies.
Consideration must also be given to providing access to and/or a means of
conveying the waste to the unit. This may require the use of conveyor belt
2-4
-------
systems, heavy field equipment (e.g., bulldozers, front end loaders) or a
liquid feed pump and piping system.
Mobilization/Demobilization. Equipment mobilization on site depends
largely on the complexity of the system (i.e., number of components
requiring field assembly). Full-scale systems generally require at least
one week to set up equipment. Multiple component systems such as rotary
kilns require several weeks. Smaller-scale (i.e., pilot, demonstration)
systems contained on a single trailer may require as few as several hours
to a day to set up. Demobilization can require as much time as
mobilization when equipment decontamination is necessary. The
decontamination that may be required ranges from operation with clean fuel
for a defined period to steam cleaning of equipment exteriors.
Residuals/Effluents. Mobile thermal treatment systems, like fixed thermal
facilities, may produce solid, liquid and gaseous waste streams. Solid
waste streams result from the incombustible portion of the original waste
stream and are removed as bottom and fly ash. Liquid residual waste
streams are generated by wet air oxidation and supercritical water
oxidation processes, and also result if wet scrubbing systems are used in
air pollution control. Gaseous effluent results from the destruction
process and is discharged by a stack after treatment by the air pollution
control system.
Depending upon the original waste stream, process residual/effluents may
require further treatment. Disposal methods for common residuals are
presented in Table 2.2.
2-5
-------
TABLE 2.2
DISPOSAL OF RESIDUALS
Residual/Effluent Disposal Method
Ash/detoxified soil/solid Depends on cleanup goals and applicable or
treatment residuals relevant regulations (e.g., delisting); may
require further treatment (e.g., immobiliza-
tion) and/or disposal in secure landfill,
sanitary landfill, or on site.
Aqueous waste streams Depends upon waste constituents; may be
(e.g., scrubber liquor, discharged to nearby municipal or industrial
separator bottoms) sewer; or may require treatment (e.g.,
neutralization, precipitation/sedimentation)
on site or off site; if treated on site, need
to address disposal of residuals (see above).
Off-gases Discharged through a stack after treatment by
air pollution control equipment to remove
particulates and acid gases. Oxygen (02) and
carbon monoxide (CO) concentrations are
continously monitored within the stack to
assure compliance with regulatory
requirements.
2-6
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2.2 ROTARY KILN INCINERATION
Process Description
Mobile rotary kiln incinerators are thermal treatment systems utilizing a
rotary kiln as the primary furnace configuration for combustion of solids.
The major components comprising a rotary kiln system typically include:
o Solids feed system,
o Rotary kiln,
o Secondary combustion chamber or afterburner,
o Air pollution control units, and
o Process stack.
Process operation involves the introduction of wastes and auxiliary fuel
into the high end of a cylindrical, refractory-lined kiln. As they pass
through the kiln, wastes are substantially oxidized to gases and ash.
Operating parameters within a mobile kiln and typical ranges are:
Temperature: 1200°F - 1800°F
Residence Time: Seconds for gases; up to hours for solids
Residence times of the feed solids within any given kiln are controlled by
four factors:
o Rotational speed of the kiln,
o Inclination of the kiln,
o Feed rate, and
o Kiln internals (e.g., dams, chains, "bellys").
Exhaust gases from the kiln enter a secondary chamber afterburner operating
at temperatures between 1400°F and 2400°F to complete oxidation of the
combustible waste. Prior to release to the atmosphere, exhaust gases from
the afterburner pass through air pollution control units for particulate
and acid gas removal. All of the existing mobile rotary kiln systems use a
scrubber as part of their air pollution control system.
Ash residue and solids are discharged at the bottom end of the kiln.
Depending upon the remaining contaminant levels, residuals may require
further treatment (such as solidification) prior to final disposal.
The application of rotary kiln technology in mobile systems is based on
extensive operating experience at fixed facilities. Operating experience
along with system configuration and processing characteristics (i.e.,
ability to handle waste in irregular physical forms including bulk solids
with -a high destruction efficiency) have established rotary kilns as a
suitable and practical candidate for use as mobile units. As of this time,
it is the only thermal technology with operating experience as a full-scale
mobile system.
A process flow diagram of a mobile rotary kiln incineration system is
presented in Figure 2.1.
2-7
-------
INJ
I
OO
SOLID WASTE
TO EJECTOR SYSTEM
TO BRINE CONCENTRATOR
RAW WATER
STACK
CONCENTRATED
BRINE SOLUTION
SOURCE: ENSCO ENVIRONMENTAL
SERVICES
FIGURE 2 . 1
PROCESS FLOW DIAGRAM OF A MOBILE
ROTARY KILN INCINERATION SYSTEM
-------
Waste Types Handled
Most types of solid, liquid, and gaseous organic wastes can be treated.
Containerized wastes and oversized debris are more difficult to handle in
smaller transportable size kilns than non-containerized wastes and
therefore must be processed to an acceptable size.
Particular wastes processed include:
o PCBs,
o Dioxins,
o Soil contaminated with organics,
o Halogenated organics,
o Nonhalogenated organics, and
o Pesticides.
Restrictive Waste Characteristics
Waste characteristics that are not suited for mobile rotary kiln systems
include:
o High inorganic salt (e.g., sodium sulfate) content which cause
degradation of the refractory and slagging of the ash, and
o High heavy metal content which can result in elevated emissions of
heavy metals which are difficult to collect with air pollution
control equipment.
Oversized debris and drums must be crushed or shredded prior to feeding.
Spherical objects that may roll through the kiln before combustion is
complete require proper feed preparation. Explosive wastes or combustible
liquid wastes in large containers (e.g., drums) should not be processed
without special evaluation, hardware designs and operator training.
Eruption of these wastes can damage the kiln or harm operating personnel.
Environmental Impacts
Process residuals may include:
o Bottom ash/soil,
o Fly ash,
o Scrubber liquor, and
o Off-gases.
Residuals may require further treatment depending upon the level of
contaminant remaining. Disposal methods for residuals/effluents are
presented in Section 2.1.
Costs
Capital costs of mobile rotary kilns will vary depending upon the system
design and size. However, in most cases, on site incineration will
probably be leased from and operated by enviromental service companies.
2-9
-------
Operating costs are dependent on the types of waste being destroyed and on
the site location. These costs are comprised principally of labor,
utilities, equipment, mobilization, decontamination, and demobilization,
and site preparation. Typical treatment costs for contaminated soil can
reportedly range from $150 to $500 per ton, again depending upon the waste
matrix, contaminants and heat value.
Commercial Applications
A large number of firms, as well as the EPA-ORD, are currently applying
rotary kiln technology as mobile systems. Mobile rotary kiln systems that
have been constructed to date have been investigated further. These firms
and agencies include:
o EPA-ORD
o ENSCO Environmental Services, Franklin, TN
o Winston Technology Inc., Lauderhill, FL
o DETOXCO Inc., Walnut Creek, CA
Other firms in the process of developing mobile rotary kiln systems
include:
o International Waste Energy Systems,
o John Zink Services, Inc.
o Rollins Environmental Services, and
o Trade Waste Incineration - A Division of Chemical Waste
Management, Inc.
EPA-ORD. The EPA-ORD has operated a mobile rotary kiln system with a
thermal capacity of 15 million Btu per hour, approximately one-fifth the
capacity of large, fixed industial installations. This unit has
successfully destroyed PCB wastes as well as a number of other RCRA-listed
wastes. The ORD unit may be available for use at other CERCLA sites.
The EPA-ORD mobile system is self-contained on three semitrailers, each
equipped with air suspension systems for reduced road shock loads. The
first trailer carries a shredder, hydraulic ram feed system, and the rotary
kiln. The second trailer carries the afterburner or secondary combustion
chamber and a water quenching system. The third trailer contains a
particulate scrubber, a mass transfer scrubber, an induced draft fan,
process stack, and a diesel-driven generator. Proposed modifications call
for replacement of the particulate scrubber with an electrostatic
precipitator. Each trailer and system configuration were specifically
designed to meet both length and weight requirements for interstate
highways.
ENSCO Environmental Services. ENSCO Environmental Services of Franklin,
Tennessee, a subsidiary of Environmental Systems Company, currently markets
a mobile rotary kiln system, the Modular Waste Processor (MWP-2000). The
company currently operates three of these commercial-scale systems. Each
unit is nominally rated at 35 million Btu per hour.
2-10
-------
The MW-2000 system is generally considered appropriate for onsite treatment
when the solid waste quantity exceeds 4,000 to 5,000 tons. 50,000 tons is
the maximum practical project size for this size system. A larger project
would dictate a custom-designed system.
Virtually any solid, liquid, slurry or sludge waste stream can be treated.
Oversized debris and drums must be crushed of shredded to two inches or
less for feeding. Wastes with high bromine, fluorine or phosphorous
content are not accepted.
ENSCO provides complete site services (e.g., excavation, incineration,
residue disposal) or will serve as a subcontractor for incineration
services only.
Winston Technology, Inc. Winston Technology Inc. of Lauderhill, Florida
has two rotary kiln systems constructed. Each unit is rated at 8 million
Btu per hour and is contained on a single tractor trailer. Winston
Technology is currently awaiting a site to conduct a test burn on this
system.
Winston Technology indicates that it is capable of providing many site
services (e.g., incineration, residue disposal, laboratory analysis). One
service not offered is excavation.
DETOXCO Inc. DETOXCO of Walnut Creek, California offers Mobile Thermal
Destruction Systems (MTD) in various sizes and capacities. These systems
are scaleups of the EPA-ORD developed mobile system.
Acceptable wastes include virtually all combustible wastes, aqueous wastes
contaminated with combustibles, and soils contaminated with combustibles.
A demonstration-scale system capable of treating 3000 Ib per hour of soil
has been constructed. Two commercial-scale mobile rotary kiln systems are
under development. DETOXCO indicates that one unit will be nominally rated
at 45 million Btu per hour and at 94 million Btu per hour. All systems are
transportable over the road via tractor trailers.
DETOXCO plans to provide complete site services (e.g., excavation,
incineration, residue disposal) or will serve as a subcontractor for
incineration services only.
More specific information on each of these firms is available in Superfund
Treatment Technologies: A Vendor Inventory (EPA, 1986).
2-11
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2.3 LIQUID INJECTION INCINERATION
Process Description
Liquid injection incinerators consist of a refractory-lined combustion
chamber and a series of atomizing devices, usually fluid (i.e., air or
steam) atomized nozzles. These devices introduce waste material into the
combustion chamber in finely divided droplets vigorously mixed with air.
Following combustion, the flue gases are cooled and treated with air
pollution control devices to remove particulates and to absorb acid gases.
Complete combustion requires adequate atomization of the waste in order to
provide for efficient mixing with the oxygen source. Pretreatment, such as
masceration and blending, may be required for wastes that may be difficult
to atomize, vary in heat content, or are not pumpable.
No mobile liquid injection systems dedicated to liquid incineration are
known to be in commercial operation. Liquid injection systems are,
however, used extensively in conjunction with mobile rotary kiln systems to
efficiently incinerate liquid wastes. Liquid injection technology is well
proven and is used by the majority of fixed hazardous waste facilities.
Therefore, this technology should be considered viable for mobile
applications, although it is limited to pumpable wastes.
Waste Types Handled
This process can be applied to almost all pumpable, atomizable organic
wastes. Particular contaminants processed include:
o Liquid PCBs,
o Halogenated organics,
o Non-halogenated organics,
o Pesticides,
o Pumpable acid and phenolic sludges, and
o Dioxins.
Restrictive Waste Characteristics
Waste chacteristics that are not suited for liquid injection systems
include:
o High inorganic salt content,
o High moisture content,
o High heavy metal content, and
o Nonpumpable sludges, solids and soils.
Wastes with high moisture content are not restricted in all cases.
Depending on the waste stream, high moisture content may be beneficial in
reducing system temperature while allowing the same thermal input. In all
cases the waste stream must be free of (or pre-processed to remove) solids
which prevent pumping and satisfactory atomization or which fuse at
incineration temperatures and attack (flux) refractory material or
sublime/vaporize to yield a hard-to-collect fume. Wastes that are
reactive, have a very low flash point, and have a substantial, fusable or
2-12
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vaporizable ash content may cause operation problems and therefore merit
special review.
Environmental Impacts
Process residuals may include:
o Bottom/fly ash,
o Scrubber liquor, and
o Off-gases.
Depending on the waste, ash may or may not be generated. For instance,
many liquid wastes will generate little or no ash. Disposal methods for
residuals/effluents are presented in Section 2.1.
Commercial Applications
As stated previously, no mobile liquid injection units dedicated to liquid
incineration are in commercial operation. Liquid injection systems are,
however, presently used in conjunction with mobile rotary kiln systems.
ENSCO Environmental Services of Franklin, Tennessee operates a full-scale
mobile rotary kiln system that utilizes liquid injectors in both the
primary (i.e., rotary kiln) and secondary combustion chambers.
2-13
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2.4 FLUIDIZED BED INCINERATION
Process Description
Fluidized bed incinerators are refractory-lined vessels containing a bed of
graded, inert granular material usually silica sand. The heated bed
material is expanded by combustion air forced upward through the bed. As
waste material is injected radially and mixed with the hot fluidized bed
material, heat is rapidly transferred to the waste feed. When the waste
dries and burns, heat is transferred back to the bed. Excess air
requirements are reduced because of the high degree of turbulence in the
bed which ensures thorough mixing between combustion gases and the waste
feed. Bed depths of fixed commercial scale sized facilities are typically
three feet while at rest and six feet during operation. Bed depths of
mobile systems are considerably less due to equipment size limitations.
Variations in the depth affect both residence time and pressure drop,
resulting in a compromised depth which optimizes residence time and excess
air to ensure complete combustion. Any inorganic materials in the waste
stream are entrapped in the bed which necessitates continuous removal and
make-up of bed material.
Secondary combustion chambers (including the freeboard volume above the
bed) are always used to give additional time for complete combustion.
Off-gas treatment following the secondary reaction chamber is dependent on
the waste feed and may include a wet scrubber, baghouse or electrostatic
precipitator (ESP).
Operating parameters for mobile fluidized bed units are:
Temperature: 1400° - 1800°F
Residence Time: Bed-minutes
Freeboard and secondary combustion
chamber-seconds
Developers have indicated that higher operating temperatures (1600°-2400°F)
are possible without causing bed defluidization problems.
A variation in fluidized bed technology has been applied to waste disposal
and is referred to as circulating bed combustion. Unlike a conventional
fluidized bed which has a fixed bed depth, high velocity air introduced at
the bottom of the refractory-lined combustion chamber transports the bed
out of the fluidization zone. Subsequently, the eluted solids are captured
and partially returned to the fluidization zone. This results in
entrainment of wastes and subsequent combustion along the entire height of
the combustion section. Complete destruction is reported to be attained at
relatively low temperatures because of this high degree of turbulance.
Secondary combustion chambers are said not to be required because of the
high degree of destruction. Off-gases pass through a cyclone which
captures and recycles solids (and perhaps, ground limestone which can be
added for acid gas control) to the combustion zone through a nonmechanical
seal. The combustion gases pass through a heat recovery system and
baghouse filter or other air pollution device prior to discharge to a
stack.
2-14
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Operating parameters for mobile circulating bed combustors are:
Temperature: 1400° - 1800°F
Residence Time: Gases - 2 seconds
Solids - minutes to hours
The application of conventional fluidized bed and circulating bed systems
to treat hazardous wastes is based on extensive operating experience for
coal, refinery sludge, paper mill sludge and sewage sludge combustion. To
date, most fluidized bed and circulating bed systems handling hazardous
wastes are fixed facilities. There is, however, a mobile,
demonstration-scale fluidized bed system operating as well as a mobile,
circulating bed combustor under design. Though their use in hazardous
waste incineration is limited, the potential applications of fluidized and
circulating bed systems for mobile units is promising.
Process diagrams of typical fluidized and circulating bed systems are
presented in Figures 2.2 and 2.3, respectively.
Waste Type Handled
Applicable wastes include organic solids, sludges, slurries and liquids.
Particular wastes that may be processed include:
o Contaminated soil,
o Halogenated organics,
o Non-halogenated organics,
o PCBs,
o Pharmaceutical wastes, and
o Phenolic wastes.
Restrictive Waste Characteristics
Waste characteristics that are not suited for fluidized bed systems
include:
o Oversized pieces of waste that cannot be shredded to less than
one inch in size for circulating bed combustors and less than
three inches for fluidized bed combustors,
o High sodium content which can cause degradation of the refractory
and slagging of the ash,
o High heavy metal content which can result in volatilization of the
metals and unacceptable emission levels, and
o Low-melting point constituents (<1600°F) that may cause operational
difficulties.
Pretreatment such as grinding and size reduction is particularly important
in order to provide a uniform character/size feed and conditions such that
solids removal from the bed is possible.
2-15
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SOLID RAW
FEED IN
INLET
RECEIVING TANK
SOLIDS FEEDER
FROM
ATMOSPHERE
AUXILARY FUEL
LIQUID FUEL
ATOMIZER
FLUIDIZED
r-i BED
* '
**»*₯ * i <
I
T
TO
ATMOSPHERE
BAQHOU8E OR
WET SCRUBBER
COMBUSTION
AIR
*o
HEAT
EXCHANGER
I
\
PREHEATED SOLIDS TO
COMBUSTION AIR WASTE DISPOSAL
SAND
STORAGE
SAND SUPPLY
IN
SPENT SAND
OUT
FIGURE 2.2
PROCESS FLOW DIAGRAM OF FLUIDIZED BED
INCINERATOR
-------
Steam/
hot water"*
Combustion
chamber
Waste fuel.
and
dry sex-bent
Liquid
wastes
Source: GA Technok>gi*s
Clean
ofl gas
Dry ash
FIGURE 2.3
SCHEMATIC DIAGRAM OF CIRCULATING BED INCINERATOR
2-17
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Environmental Impacts
Process residuals may include:
o Bottom fly ash,
o Scrubber liquor, and
o Off-gases.
Disposal methods for residuals/effluents are presented in Section 2.1.
Costs
Capital costs of mobile fluidized and circulating bed systems will vary
depending upon the system design and size. Operating costs are comprised
principally of labor, utilities, equipment mobilization, decontamination,
and demobilization, waste pretreatment and site preparation. These costs
will vary widely depending on the waste being destroyed. Hazardous waste
treatment costs for mobile fluidized bed systems are reported to range from
$600 to $1500 per ton. Treatment costs for mobile circulating bed systems
have been reported to be over $250 per ton.
Commercial Applications
Relatively few companies are currently applying fluidized and circulating
bed technologies as mobile systems to treat hazardous waste. The two most
active firms developing these technologies for hazardous waste treatment
are Waste-Tech Services Inc. and GA Technologies Inc.
Waste-Tech Services .Inc. Waste-Tech Services of Lakewood, Colorado
operates a demonstration-scale mobile fluidized bed system. The complete
system is comprised of a fluidized bed, secondary reaction chamber (SRC)
and an off-gas treatment system. The mobile system can handle organic
solids, liquids, sludges and soil. Wastes with high sodium and heavy metal
content are restricted as are wastes containing fluorinated compounds.
Solids must be shredded to less than three inches in size.
Larger scale mobile units are under development. Thermal capacities of
these systems will range from 20 to 40 million Btu per hour. Construction
will occur only when service contracts are signed.
Additional technical information is available in the Superfund Treatment
Technologies; A Vendor Inventory (EPA, 1986).
GA Technologies Inc. GA Technologies of San Diego, California is presently
designing a mobile circulating bed combustor (CBC) with an internal
diameter of three feet. The system will consist of a series of
interconnected modular units. The modular units contain both the plant
components as well as the structural support members.
The proposed system has a thermal capacity of nine million Btu per hour.
It will be designed to process approximately five tons per hour of soil and
approximately 600 Ibs per hour of liquid hydrocarbons. Solid, liquid, and
sludge waste streams can be treated. Solid waste streams must be reduced
to less than one inch ring size for feeding.
2-18
-------
GA Technology can provide complete site services including excavation,
incineration, and residue disposal.
Additional technical information is available in Superfund Treatment
Technologies; A Vendor Inventory (EPA, 1986).
2-19
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2.5 INFRARED INCINERATION
Process Description
Infrared incineration systems are designed to destroy hazardous wastes
through tightly controlled process parameters with infrared energy as the
auxiliary heat source, as required. Wastes are conveyed through the
furnace for a very precise residence time on a woven metal alloy conveyor
belt which passes the wastes under infrared heating elements, equally
spaced over the length of the ceramic fiber insulated furnace. At the
discharge end of the furnace, ash residue is discharged to a hopper from
which it is then conveyed to the collection system.
Off-gases from the primary furnace are exhausted to a secondary chamber
equipped with a propane-fired burner or infrared heating elements to ensure
complete combustion of any remaining organics. Before discharge to the stack,
exhaust gases from the secondary chamber pass through air pollution control
equipment for removal of particulates and other emissions such as HCl and SO.
One firm currently markets this technology. They report the following
operating parameters:
Primary chamber: Temperature 500°-1850°F
Residence time 10-180 minutes
Secondary chamber: Temperature 1000°-2300°F
Residence time 2.2 seconds
The application of infrared incineration as a mobile technology has limited
operating experience; however, there are a number of fixed infrared units
that have been constructed. These units have primarily been used in
industrial applications. The only mobile unit being applied to hazardous
waste at this time is a pilot-scale system. However, several full-scale
commercial systems for hazardous waste treatment will soon be available.
A process flow diagram of an infrared incineration system is presented in
Figure 2.4.
Waste Type Handled
Most types of solid, liquid sludge, and gaseous organic wastes can be
treated with the total system (i.e., primary and secondary combustion
chambers) concept. Particular contaminants and wastes processed include:
o PCB wastes,
o Contaminated soils,
o Dioxin wastes, and
o Spent activated carbon.
Restrictive Waste Characteristics
Wastes must be at least 22 percent solids prior to feed. Solids that
cannot be ground or shredded to maximum size of one to one and a half
inches cannot be properly processed in this system.
2-20
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MATERIAL PROC E S S 1 NG/ D E- W A TE R IN G
O
AIR POLLUTION CONTROL
EQUIPMENT
(?§.
SECONDARY COMBUSTION
CHAMBER
AIR PRE-HEATERfOPT/OAMU
BLOWER
BLOV/ER
Mod
MATERIAL
HOLDING TANK
. .
. J3LL
A\ Vv
METERING
_/
1
J
*3
^i
£==3
II
'sc ^ _. Sl^r.T^'
r ^
1
ASH DISCHARGE
PRIMARY COMBUSTION CHAMBER
ASHIDISPOSA
O O Ji JL
SOURCE: SHIRCO INFRARED SYSTEMS INC.
FIGURE 2.4
PROCESS FLOW DIAGRAM OF INFRARED INCINERATION SYSTEM
-------
Environmental Impacts
Process residuals may include:
o Bottom ash/detoxified soil,
o Fly ash,
o Scrubber liquor, and
o Off-gases.
Disposal methods for residuals/effluents are presented in Section 2.1.
Costs
Current capital cost for a 100 ton-per-day mobile infrared system are
reported to be approximately $2,500,000. These costs include:
o Primary infrared furnace,
o Secondary afterburner,
o Off-gas handling,
o Scrubbing,
o Monitoring,
o Power supply, and
o Transport systems.
Typical direct operating costs for this unit are reported to be below $110
per ton; the actual cost depends on the organic concentration in the
wastes. The operating costs include:
o Onsite electrical power usage,
o Supplementary fuel costs,
o Chemical costs,
o Maintenance materials,
o Labor,
o Direct operating labor and supervision,
o System set-up, compliance testing, and
o System removal.
Commercial Applications
The only company at this time manufacturing infrared technology for mobile
hazardous waste treatment is Shirco Infrared Systems Inc. of Dallas, Texas.
Shirco currently operates a mobile pilot-scale unit capable of processing
approximately 100 Ibs per hour of wastes. Shirco reports that full-scale
units with nominal capacities of 100 tons per day are currently under
construction. The 100 ton per day system will use the same operating and
process configuration as the pilot-scale system. Additional pilot-scale
units are also under construction.
Shirco offers equipment manufacturing, sales and service as well as
permitting assistance. They do not plan to own or operate any full-scale
mobile systems. Four firms have contracted with Shirco to purchase
full-scale 100 ton per day systems. One firm, Haztech of Decature, Georgia
reports that delivery of their unit is scheduled for October 1986. The
other companies, OH Materials of Findley, Ohio, MAECORP Inc. of Homewood,
2-22
-------
Illinois, and Reidel Environmental Services of Portland, Oregon report that
their systems will be available in the spring of 1987. All tour lirms
intend to provide complete site services including investigation,
excavation, incineration, and residue disposal. In addition, Shirco has
entered into a limited joint venture with A&S Environmental Recovery of Los
Angelas, California. A&S will act as Shirco's agent on demonstration
programs in California. Shirco will own and operate the pilot unit.
Additional technical information is available in Superfund Treatment
Technologies; A Vendor Inventory (EPA, 1986).
2-23
-------
2.6 PLASMA ARC
Process Description
The principle of plasma arc technology involves breaking the bonds between
organic consitutents. This is accomplished in an atomization zone where a
co-linear electrode generates a plasma or electric arc that is stabilized
by field coil magnets. As low pressure air passes through the arc, the
electrical energy is converted to thermal energy by the activation of air
molecules into their ionized atomic states. When the excited atoms and
molecules relax to lower energy states, intense ultraviolet light is
emitted. The energy from the decaying plasma is transferred to passing
atomized waste materials reducing them to their elemental constituents. An
equilibrium zone is provided for the controlled cooling and recombination
of the atomic species to form simple non-hazardous molecules such as
hydrogen, carbon, carbon monoxide and hydrogen chloride.
Process units comprising a plasma arc system include:
o Plasma generator,
o Reactor vessel consisting of atomization and equilibrium zones, and
o Air pollution control equipment.
System operation parameters include:
o Atomization zone Temperature >10,000 F
Residence time 500 microseconds
o Equilibrium zone Temperature 1700-2700 F
Residence time 1-2 seconds
Since the process is pyrolytic (i.e., takes place in absence of oxygen),
the scale of the equipment is small considering the high throughput rates.
This characteristic makes it potentially attractive for use as mobile unit.
The application of plasma arc technology to hazardous waste treatment is
hindered by a lack of operating experience. At this time, the only
operating plasma arc system that is beyond the research and development
stage is a pilot-scale mobile unit.
A process schematic of a plasma arc system is presented in Figure 2.5.
Waste Type Handled
This process is applicable to liquid (pumpable) organic wastes and finely
divided, fluidized sludges. It may be particularly applicable to the
processing of liquid wastes with a high chlorine content. Contaminants
processed include:
o PCBs,
o Chlorinated organics, and
o Other complex organics.
2-24
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PROCESS WATER
Of F GASES TO FLARE
D
GAS CHROMATOGRAPH-
MASS SELECTIVITY UNIT
COOLING WATER
LABORATORY
ANALYSIS
EQUIPMENT
GAS CHROMATOGRAPH
SALT WATER TO DRAIN
SOURCE: PYROLYSIS SYSTEMS, INC. (NOW WESTINGHOUSE PLASMA SYSTEMS)
FIGURE 2.5
SCHEMATIC DIAGRAM OF PLASMA ARC SYSTEM
2-25
-------
Restrictive Waste Characteristics
Sludges must be capable of being fluidized by the addition of a liquid.
Waste streams must be free of (or pre-processed to remove) solids, which
prevent satisfactory atomization.
Environmental Impacts
Process residuals include product gas and scrubber water. Product gas is a
mixture of hydrogen, methane and other combustible gases that is
electrically ignited in a flare stack incorporated into the process.
Disposal alternatives for scrubber water are presented in Section 2.1.
Costs
It has been reported that the projected capital cost for a mobile unit
designed to process 1500 pounds of waste per hour is $1,600,000. Operating
costs have been projected by developers to range from $300 to $1400 per
ton, depending upon the waste.
Commercial Applications
There has been no commercial application of plasma arc technology in waste
disposal. The only company actively developing this technology for mobile
systems is Westinghouse Plasma Systems of Madison, Pennsylvania, a division
of Westinghouse Electric Corporation. Westinghouse Plasma Systems was
formed recently when Westinghouse's Waste Technology Services Division
joined forces with Pyrolysis Systems Inc.
A mobile pilot-scale system developed by Westinghouse Plasma Systems has
been tested on PCB wastes in Canada. The unit is owned by the New York
State Department of Environmental Conservation (NYDEC) and is scheduled to
be demonstrated at a Superfund site at Love Canal. The pilot unit is
contained in a single 45 foot van trailer and can process 1 gallon per
minute of waste. An additional full-scale unit is under development by
Westinghouse that will process 3 gallons per minute.
Arc Technologies Company is also developing plasma arc technology, although
the unit under construction is not mobile. Arc Technologies is jointly
owned by Electro-Pyrolysis Inc. of Wayne, Pennsylvania and Chemical Waste
Management of Oak Brook, Illinois. The prototype unit under construction
is specifically designed for PCB-contaminated wastes. The unit has a
capacity of 1.5 tons per hour and is being constructed at Chemical Waste
Management's Model City, New York facility.
2-26
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2.7 ADVANCED ELECTRIC REACTOR
Process Description
An advanced electric reactor (AER), also known as a high temperature fluid
wall (HTFW), is a relatively new thermal technology being developed
specifically for the detoxification of contaminated soils, although other
solid and liquid wastes may also be destroyed. The AER is distinguished
from other thermal destruction technologies in that energy is transferred
to the incoming waste through radiation instead of through combustion,
conduction or convection. Destruction is achieved by thermolysis (i.e.,
pure heating) at high temperatures in a reactor vessel where materials are
reported to break down to carbon, carbon monoxide and hydrogen.
The reactor vessel consists of a porous carbon core surrounded by carbon
electrodes. Electrical energy heats the core to high temperatures. The
core and electrodes are enclosed by a radiation heat shield constructed of
multiple layers of graphite paper backed with carbon felt. The heat shield
is in turn surrounded with more conventional insulation and a double wall
cooling jacket. Reactants are isolated from the reactor core by a gaseous
blanket formed by nitrogen flowing radially inward through the porous core
wall. The inert gas also serves as a heat transfer medium between the
electrodes and the core.
For solid waste treatment, process operation involves introducing the
solid feed at the top of the reactor with a metered screw feeder. The
wastes pass through the core via gravity where thermolysis occurs at
approximately 4000°F. The exit gases and waste solids from the reactor
then enter two post-reactor treatment zones to ensure complete destruction.
After passing through these zones, the remaining solid residue is collected
in a bin. Exit gases pass through air pollution control equipment for
removal of particulates and other emissions prior to discharge.
An important characteristic of this process reportedly is the AER's
transportability potential. Because this technology has been specifically
designed for the detoxification of contaminated soils, a major effort has
been expended to apply these units to onsite treatment. The application of
AER technology is restricted by the limited operating experience.
Operation to date has been limited to pilot systems. No full-scale systems
have been constructed. Two of the pilot systems are mobile. Results from
these units indicate that full-scale technology may soon be commercially
available.
A schematic diagram of an AER system is presented in Figure 2.6.
Waste Types Handled
This process can be applied to solid, liquid and gaseous wastes. Wastes
with low Btu content such as contaminated soils are acceptable. Particular
wastes processed include:
o Contaminated soil, o Heavily halogenated organics, and
o PCBs, o Nerve gas.
o Dioxins,
2-27
-------
Air tight hopper
for feed
Makeup water
and NaOH
Stack
SOURCE: J.M. HUBER COMPANY
FIGURE 2.6
SCHEMATIC DIAGRAM OF HUBER ADVANCED ELECTRIC REACTOR
_
-------
Restrictive Waste Characteristics
Solids must be reduced to 35-mesh particle size (analogous to fine sand)
and liquids must be atomized to no larger than 1500-micron droplets.
Pretreatment with grinders and/or crushers is often required to provide a
uniform feed to the system. Sludges cannot be handled by the AER. A
suitable feed system for sludges has not been developed.
Environmental Impacts
Process residuals may include:
o Bottom ash/decontaminated soil,
o Fly ash,
o Scrubber liquor, and
o Off-gases.
Disposal methods for residuals/effluents are presented in Section 2.1.
Commercial Applications
The HTFW technology was originally developed by Thagard Research
Corporation of Irvine, California. Thagard has since sold the patents to
the process to J.M. Huber Corporation of Borger, Texas while remaining a
licensee of the technology. Huber has made proprietary changes to the
basic technology and markets their process under the trade name Advanced
Electric Reactor. Huber currently operates two mobile pilot-scale units.
One unit has a core diameter of three inches and a capacity of 30 Ibs per
hour. The other mobile system has a 12-inch core diameter and a capacity
of 3000 Ibs per hour. System components for both units include:
o Pretreatment system (e.g., crushers, grinders, dryer),
o Liquid storage tank and pump,
o Reactor vessel, and
o Air pollution control units (e.g., cyclone, packed bed scrubber,
baghouse, activated carbon filters).
In addition to the 3- and 12-inch diameter units, Huber is constructing a
6-inch diameter AER. An engineering design has also been completed on a
full-scale mobile system. Huber anticipates that this system will require
four to six weeks for transport and set up. A level 200 square foot
staging area will be necessary for system set up.
Huber indicates that they do not presently supply excavation, waste
transportation, residue disposal or analytical services. However, these
services can be supplied by subcontractors.
Additional technical information is available in Superfund Treatment
Technologies: A Vendor Inventory (EPA, 1986).
2-29
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2.8 SUPERCRITICAL WATER OXIDATION
Process Description
The supercritical water oxidation process is based on the ability of water
to perform as an excellent solvent for organics when the water is above its
critical temperature (705°F) and critical pressure (3200 psi). When air is
mixed with aqueous wastes above the critical temperature and pressure of
water, organics are reported to be rapidly and completely oxidized to C09
and water. In addition, inorganic salts become almost insoluble above
930 F and precipitate out of the supercritical liquid. The exothermic
conditions during the oxidation reactions produce energy in excess of
process energy requirements and, in principle, allow for the production of
high pressure steam or electricity.
Process operation involves the use of a high pressure pump to bring an
aqueous solution or slurry of hazardous wastes up to system pressure before
being heated to supercritical conditions in a feed/effluent heat exchanger.
Large organic molecules are thus broken down to molecules of low molecular
weight. High pressure air is then injected into the reactor, rapidly
oxidizing the lower molecular weight compounds. Bases such as sodium
hydroxide are added to the waste to neutralize any inorganic acids formed
during oxidation.
The supercritical water oxidation process can be adapted to a wide range of
feed mixtures and scales of operation, making it a potentially feasible
mobile technology. However, supercritical water oxidation is a relatively
new thermal technology and therefore has limited operating experience. To
date, operating experience has been restricted to bench-scale and pilot-
scale systems. The pilot-scale system is skid-mounted and capable of being
transported. Commercial-scale systems are reportedly under design.
A process flow diagram is presented in Figure 2.7.
Waste Type Handled
This technology can be applied to aqueous solutions or slurries with
organic concentrations from 1 to 100 percent. The actual organic
concentration of the waste fed to the process will depend on the heating
value of the original waste material. The heat content of waste fed to the
process is controlled at 1800 Btu per Ib. Therefore, wastes with a heating
value below 1800 Btu per Ib require the addition of auxiliary fuel. Waste
material with a heating value .above 1800 Btu per Ib requires either the
addition of dilution water or blending with a lower heating value waste.
Particular contaminants and wastes processed include:
o PCBs,
o Dioxins,
o Solvents,
o Pesticides, and
o Still bottoms and tank bottoms.
2-30
-------
ro
i
CO
VAPORIZER
FEED
REACTION AND
SALT SEPARATION
COOLING AND
HEAT RECOVERY
GAS
GAS-LIQUID
SEPARATOR
LIQUID
(WATER)
SALTS
PRESSURE LETDOWN
AND EFFLUENT DISCHARGE
SOURCE:
MODAR, INC.
FIGURE 2.7
PROCESS FLOW DIAGRAM OF
SUPERCRITICAL WATER OXIDATION PROCESS
-------
Restrictive Waste Characteristics
Non-pumpable wastes are restricted from this process.
Environmental Impacts
Process residuals/effluents include inorganic salts (solids), aqueous
separator bottoms and carbon dioxide. Disposal methods for
residuals/effluents are presented in Section 2.1.
Commercial Applications
MODAR, Inc. is the only firm marketing supercritical water oxidation
systems. In addition to a bench-scale unit, MODAR operates a mobile pilot-
scale system. The mobile unit is skid-mounted and can process up to 1000
gallons of dilute organic wastes per day. MODAR reports that the first
commercial-scale system is currently being designed. It can be
transported, but the intent is that the first system be designed
site-specifically. Its capacity will be 10,000 to 30,000 gallons per day
of 10 percent organics in water.
MODAR reports that it now offers stationary and transportable units with
capacities ranging from 50 to 250 gallons (organic content) per day and
eventually plans to offer stationary units up to 25,000 gallons (organic
content) per day. Transportable systems will be available with capacities
from 50 to 1250 gallons (organic content) per day.
MODAR does not sell hardware nor act as a service contractor. The firm
leases supercritical water oxidation units with full operating and
maintenance staff to clients.
Additional technical information is available in Superfund Treatment
Technologies; A Vendor Inventory (EPA, 1986).
2-32
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2.9 WET AIR OXIDATION
Process Description
Wet air oxidation is a thermal treatment technology which breaks down
organic materials by oxidation in a high temperature and pressure aqueous
environment and in the presence of compressed air. The resulting
exothermic reactions are self-sustaining and potentially capable of
generating steam as a by-product.
In this process, wastes are mixed with compressed air. The waste-air
mixture is then preheated in a heat exchanger before entering the
corrosion-resistant reactor where exothermic reactions increase the
temperature to a desired value. The exit stream from the reactor is used
as the heating medium in the heat exchanger before it enters a separator
where the spent process vapors (i.e., non-condensible gases consisting
primarily of air and carbon dioxide) are separated from the oxidized liquid
phase.
The reactor or pressure vessel is sized to accommodate a specific waste
flow over a certain amount of time. Residence time, temperature, pressure
and possibly a catalyst are based upon the characteristics of the waste.
Wet air oxidation technology has been used extensively for industrial
applications. Utilization of this technology for hazardous waste is more
limited. There are, however, several full-scale fixed facilities treating
hazardous waste. System configuration and size make wet air oxidation
systems suitable for skid-mounting. Use of this technology as mobile
systems therefore appears favorable.
A process flow diagram for wet air oxidation is presented in Figure 2.8.
Waste Types Handled
This process can be applied to dissolved or suspended organic substances in
the form of liquid wastes and sludges.
Particular contaminants and wastes processed include:
o Halogenated organics,
o Inorganic/organic sludges,
o Contaminated groundwater,
o Inorganic/organic cyanides,
o Phenols, and
o Leachates.
Restrictive Waste Characteristics
Non-pumpable aqueous wastes and highly halogenated wastes are restricted
from this process. Minimum and maximum chemical oxygen demand (COD)
concentrations for a feasible application are 10,000 milligrams per liter
and 200,000 milligrams per liter, respectively.
2-33
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ro
i
OJ
OXIDIZABLE
WASTE
FEED
PUMP
PROCESS
HEAT
EXCHANGER
AIR
COMPRESSOR
IIMIIIIIIIItlllMU D{* yiMIIHtHIIIIHIIMIMmt
REACTOR
PCV
OXIDIZED
WASTEWATER
SOURCE : ZIMPRO, INC
FIGURE 2.8
PROCESS FLOW DIAGRAM OF WET AIR OXIDATION
-------
Environmental Impacts
Process residuals include aqueous, treated effluent comprised of
biodegradeable, short-chain molecular organics. The liquid effluent can be
treated on site in a separate biotreatment system for discharge to a stream
or municipal sewer or, if within acceptable biochemical oxygen demand (BOD)
and COD levels, can be directly discharged to a municipal sewer. Gaseous
pollutants are not usually produced. However, aldehydes formed in the
process may create odor problems if they are not handled carefully.
Costs
Current capital cost for a 10 gallon per minute mobile wet air oxidation
unit is reported to be $1,500,000. Treatment costs reportedly range from
six to seven cents per gallon.
Commercial Applications
Zimpro Inc. of Rothschild, Wisconsin has developed and marketed wet air
oxidation technology for industrial and hazardous waste application.
Zimpro currently has three full-scale mobile units for hazardous waste
treatment with additional commercial units under development. Each
full-scale system is skid-mounted and has a nominal capacity of 10 gallons
per minute. Actual flow rates depend on the COD of the waste material.
System components include:
o Heat exchangers,
o Reactor,
o Gas-liquid separator,
o Air compressor,
o Positive displacement pump,
o Gas-carbon adsorption, and
o Pressure reducing system.
Each unit is transportable on a standard flat-bed trailer. System set up
requires a 1400 square foot concrete pad and takes approximately four days.
Zimpro indicates that it can provide complete site services such as
excavation, waste transportation, thermal treatment, and residue disposal.
Additional technical information is available in Superfund Treatment
Technologies; A Vendor Inventory (EPA, 1986).
VerTech Treatment Systems of Denver, Colorado is also developing mobile wet
air oxidation systems. Development to date has been limited to bench-scale
testing. A mobile demonstration-scale system is currently under design.
VerTech reports that their systems will be commercially available in
various sizes in 1987.
2-35
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-------
3.0 IMMOBILIZATION
Introduction
The method of waste treatment discussed in this section is described by
terms such as stabilization, solidification, fixation and immobilization.
In general, all of these terms refer to the process of adding materials
that combine physically and/or chemically to decrease the mobility of the
original waste constituents. The end result of this process is to retard
further migration of contaminants. Because of the similarities among the
terms listed above, they are all referred to in this section by one general
term immobilization.
Immobilization is used for several purposes which include the following:
o Improvement of waste handling characteristics,
o Solidification of liquid phases and immobilization of any highly
soluble components,
o Reduction in the potential contact area between the waste and any
liquids that may come in contact with the waste to minimize leaching
potential, and
o Detoxification of the waste.
The process of fixation can achieve the above objectives, but the
application of a specific process is dependent upon the final disposal
method to be used for the waste. Some applications include:
o In situ immobilization - useful for reducing potential contaminant
migration into groundwater without excavation,
o Excavation and partial immobilization - useful for improving waste
handling characteristics and solidifying liquid phases prior to
disposal in a secure landfill,
o Excavation and full immobilization - used to convert waste to a
solid mass with more complete immobilization of soluble
contaminants. Tests are required to demonstrate that such
immobilization meets remedial action goals.
The applications above are listed in order of increasing cost. The cost is
directly linked to the quantity of fixing agent (typically cement) used.
Final disposal options for more complete immobilization may be less
expensive than those for wastes that are partially immobilized. Disposal
costs should be considered when determining the use of immobilization
methods.
Portland cement is widely used for immobilization because of its ready
availability. Pozzolanic materials such as fly ash may be available at a
lower cost, but the regulations on land disposal of hazardous bulk liquids
prohibit the use of materials such as fly ash that do not fully immobilize
3-1
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the waste. The use of a immobilization technique should be made only after
the immobilization process has been tested on sample material and the
chemical and physical properties of the solidified waste have been
extensively tested to insure that contaminant immobilization is adequate.
Vendors of immobilization processes will usually conduct pilot tests on
sample material to ensure their process performs adequately.
Other immobilization techniques such as encapsulation in asphalt or glass
are available. However, the vast majority of mobile immobilization systems
are cement- or pozzolan-based. Hence only these types of immobilization
are discussed in this section.
Process Description
The equipment required for this treatment includes standard cement mixing
and handling equipment which is widely available. The techniques of cement
mixing and handling are well-developed and the process is reasonably
tolerant of variations in the waste stream and/or soil matrix. However,
modifications to the process include the use of more expensive cement
types, and costly additives or coatings. In situ immobilization may
require the use of special subsurface fixative injection equipment.
The key operation parameters include:
o Fixative-to-waste ratio (usually 1 to 1),
o Length of time for setting and curing (usually one to two days), and
o Required structural integrity and minimized potential for leaching
of the pollutants from the resultant solidified waste mass.
Immobilization procedures are quite mobile. Heavy equipment such as
backhoes, specialized hydraulic augers, cement mixers and dump trucks are
used for specific excavation, mixing and hauling needs. Many companies
have developed specialized equipment such as injectors and augers that
simultaneously inject cement and mix the matrix.
Wastes Types Handled
Immobilization is well-suited for solidifying sludges and soils containing
the following:
o Heavy metals,
o Inorganics such as sulfides,
o Organics (generally no more than 20% by volume),
o Asbestos, and
o Solidified plastic, resins and latex.
Use of sodium silicates can reduce interference with dissolved metallic
anionic species such as arsenate and borate.
3-2
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Waste Restrictive Characteristics
The following constituents may interfere with the use of cement-based
methods of immobilizing of hazardous constituents:
o Fine organic particles such as silt, clay, lignite or other
insoluble materials passing the No. 200 sieve. These particles can
weaken cement bonds by coating large contaminants with a dust layer;
o Elevated levels of organics such as solvents can interfere with
setting and curing of cement-based fixatives. Some vendors have
processes that can handle up to 100% organics, but 20 to 40%
organics is a more typical maximum;
o Soluble salts of many metals (i.e., manganese, tin, zinc, copper,
lead) as well as the sodium salts of arsenate, borate, phosphate,
iodate and sulfide. These salts interfere with the setting and
curing of cement as well as reduce the ultimate strength of the
product;
o Sulfates which retard the setting of concrete as well as cause
swelling due to the formation of calcium sulfoaluminate hydrate.
Required Onsite Facilities/Capabilities
Because heavy equipment will be used on site, project managers must
consider the required access roads, adequate safety during operation and
decontamination of equipment.
As the operation is progressing, quality control should be incorporated to
insure that proper mixing ratios and proper solid consistency are achieved,
thus minimizing the leaching potential of the final fixed product. This
may require onsite (or nearby offsite) testing using a field laboratory.
Chemical storage facilities would also need to be provided.
Environmental Impacts
The following environmental concerns are associated with immobilization
technologies:
o Sidestreams generated in this process include leachate water which
may be produced as a result of the drying process. However, the
volume is usually minimal and storage and later disposal may address
this problem.
o The alkalinity of cement drives off ammonium ion as ammonia gas.
Therefore, gas monitoring and collection may be necessary with
wastes containing ammonium ion.
o Site-specific requirements that may hinder implementation include
space limitations for disposal (immobilized waste volume may double)
or an acidic in situ leaching medium.
3-3
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Applicable regulatory requirements may include RCRA requirements
pertaining to treatment of hazardous waste and RCRA delisting
requirements if disposal as a sanitary waste is desired.
The movement of treated wastes off site may significantly degrade
existing roads, create a dust problem, and impact nearby residents
due to the noise and inconvenience of heavy equipment nearby.
Prevention of offsite transfer of contaminants by vehicles should
include decontamination by high pressure steam prior to any vehicle
departing the site.
Costs
Information supplied by vendors (Superfund Treatment Technologies - A
Vendor Inventory, EPA, 1986) typically estimate the cost of cement-based
treatment at $0.10 to $0.35 per gallon or $25 to $150 per cubic yard. The
highest estimated cost is quoted by a vendor principally treating
radioactive wastes. The highest cost method of immobilization is total
encapsulation of waste. Guidelines to the costs for treatment are
presented in Table 3-1.
In most cases, the desired method of disposal will dictate the degree, and
therefore, the cost of treatment. For landfilling, cost of disposal is
usually a function of the bulk of materialsthe greater the bulk, the
higher the cost. Use of Portland cement may produce an increase in bulk of
100 to 250 percent though several vendors have processes that produce
smaller volume increases. Cost of disposal in a landfill will increase
accordingly. Conversely, thorough immobilization of the waste so that it
can be delisted may permit disposal in a sanitary landfill instead of a
hazardous waste landfill. This would result in substantial savings in the
cost of landfilling.
Commercial Applications
Few vendors are willing to identify the type or amount of additives
employed in immobilization treatments. The type and amount of additives
vary depending on the wastes being treated and in many cases, information
concerning these additives is proprietary. The vendors universally prefer
to determine treatability after sampling the wastes and subjecting the
samples to laboratory testing. Many vendors restrict their activities to
particular waste types.
A summary of information supplied by vendors for the Superfund Treatment
Technologies - A Vendor Inventory (EPA, 1986) is presented in Table 3-1.
Company contacts and addresses can be found in the appendix.
3-4
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TABLE 3.1
MOBILE IMMOBILIZATION PROCESSES
Company
Chemfix Technologies,
Inc.
Kemer, LA
Chemical Waste
Management
Riverdale, IL
Envirite Field
Services
Plymouth Meeting, PA
Hazcon Inc.
Katy, TX
OJ
i
O1
Sol idtek
Morrow, GA
Type of
Mabil Equipment Processing Rate
Mixer, materials 50 to 800 gpm
handling equip.,
excavations
Conventional heavy Varies
equipment, mixers,
materials handling
equipment
Proprietary dewater- 25,000 to 90,000 gpd
ing and chemical
injection equipment
Proprietary mixing, 5 to 60 cy/hr.
dredging and
conveyor equipment
Proprietary special 5 to 200 cy/hr.
purpose machinery
In Situ Types of
Capability Wastes Preferred
No Aqueous, <60$
solids
No Solids,
sludges,
liquids
Yes Solids, sludges,
liquids
No Organics up to
100 % oily
sludges, metals
NO NO restrictions
Fixation
Agent
Proprietary
Varies
Unspecified
Cement and
proprietary
agents
unspeciTieu
Time to Guideline Cost
Mobilize of Treatment
2 weeks $20 to $50/ton
2 days
< 1 day $0.10 to $0.25/gal
12 hours $65 to $150/cy
o on Ha we
End Product
A friable clay-like
product
Unstated
Stabilized landfillable
material
Solid, 1,000- 5,000 psi
conpr. strength.^
permeability 10" ,
\/3p~i PC JVffincH nn tn
Vul 1 CD u^A*UI VJ H ly \AJ
specifications and method
Velsicol Chemical Corp. Mixers, excavators, Varies
Msmphis, TN bulldozers
Westinghouse Hittman
Nuclear
Colinbia, MD
Proprietary ccnv- Batch: 150 to 300 gph
pacting, mixing, and Continuous: 5 to 15 gpm
silo equipment
Yes Organics up to Cement and
45%, sludges unspecified
chemicals
No Liquids, semi- Cement
solids
3.4 weeks $0.15 to $0.50/gal
1-2 weeks $1350 - $2200/cy*
Stabilized, heavy clay
like substance
Solidified mass with
high structural
integrity
ATW/Caldweld
Santa Fe Springs, CA
Custom augering, 100-150 cy/hr.
mixing and injection
equipment with full
in situ monitoring
systems
Yes
Solids and
soils
Fixation
oxidation,
precipitation,
and biological
agents may
be injected
1-2 weeks
Stabilized or solidified
mass in subsurface
* Stated costs of treatment is for radioactive wastes. No costs quotpd for hazardous waste.
-------
-------
4.0 CHEMICAL TREATMENT TECHNOLOGIES
4.1 INTRODUCTION
This section describes the applications and restrictions of mobile chemical
treatment technologies for the cleanup of hazardous waste sites. These
treatment technologies are widely used in industrial waste treatment and
pretreatment. Thus, more complete descriptions of the processes can be
found in the literature.
Chemical treatment processes alter the chemical structure of the
constituents to produce a waste residue that is less hazardous than the
original waste. Further, the altered constituents may be easier to remove
from the waste stream. The chemical treatment processes presented in this
section are defined below.
o Chemical reduction-oxidation (redox) treatment - the chemical
transformation of reactants in which the oxidation state of one
reactant is raised while the other is lowered.
o Neutralization - the interaction of a acid or base to adjust the pH
of a solution or mixture to between pH 5 and 9.
o Precipitation - physical/chemical process in which a dissolved
contaminant is transformed into an insoluble solid and then removed
by flocculation and sedimentation.
o Dechlorination - the addition of a chemical to remove the chlorine
atoms from a hydrocarbon.
Treatment sludges from any of these processes may require additional
treatment either on site or off site prior to disposal. Treatment needed
may include dewatering (and subsequent treatment of water) and immobili-
zation. Depending upon the applicable requirements, solid residuals can be
disposed of on site or off site.
4-1
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4.2 CHEMICAL REDUCTION-OXIDATION (REDOX) TREATMENT
Process Description
Reduction-oxidation (redox) reactions involve the chemical transformation
of reactants in which the oxidation state of one reactant is raised while
the other is lowered. The process destroys or reduces the toxicity of many
toxic organics and heavy metals.
Use of reducing agents for treatment is less common than oxidizing agents
because of the high reactivity of the reducing agents. Agents that are
generally used for redox treatment include:
Oxidizing Agents Reducing Agents
Ozone Ferrous sulfate
Hypochlorite Sodium sulfate
Hydrogen peroxide Sulfur dioxide
Chlorine Iron (+2)
Potassium permanganate Aluminum
UV/ozone Zinc
Sodium borohydride
To ensure a complete reaction between the reactants and agents, there are
specific requirements for the pH of the solution, chemical additions and
rapid mixing. Some of these requirements are:
o Adequate contact between the reagents and the contaminants is
crucial for an efficient chemical reaction. Therefore, special
precautions must be used when applying reagents to solid materials,
such as soils.
o Strong oxidizers do not discriminate between natural organics and
contaminants; thus an excess amount of applied agents may be
required if natural organics are present.
o Narrow pH ranges need to be maintained for optimum reaction rates.
Oxidation-reduction potential (ORP) electrodes are used to monitor the
progress of this reaction.
Figure 4.1 shows a typical oxidation system for the chemical reduction of
hexavalent chromium.
The equipment requirements for aqueous waste treatment are relatively
simple. Potential equipment needs include:
o Enclosed cylindrical tanks with rapid mix agitators to serve as the
reaction vessels;
o Controls such as pH meters, oxidation-reduction potential (ORP)
electrodes, and metering pumps; and
o Storage tanks for reagents and pH adjustment materials.
4-2
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-pi
I
GO
TO FILTRATION/
SEDIMENTATION
MIXING TANK
MIXING TANK
FIGURE 4.1
SCHEMATIC DIAGRAM OF CHEMICAL REDUCTION OF HEXAVALENT CHROMIUM (Cr 6+)
-------
Slurries and soils may require larger reaction vessels and longer detention
times than aqueous wastes. In situ methods of treatment require subsurface
injection of reagents and water to contain possible violent reactions.
Waste Type Handled
Redox reactions are applied to a number of different contaminants; either
oxidizing agents or reducing agents are applied to the waste in separate
reaction vessels.
Redox treatment has most commonly been applied to aqueous wastes containing
heavy metals. For example, water used to flush source material from soils
may be treated via redox reactions.
Efforts have recently focused on applying redox treatment to slurries,
sludges and soils. Applying a water-reagent mixture to sludges and soils
will aid in mixing. In addition, combining this treatment with a soil
flushing system may improve performance.
Wastes that can be treated via redox include:
Oxidation Treatment Reduction Treatment
Benzene Chromium (VI)
Phenols Mercury
Most organics Lead
Cyanide Silver
Arsenic Chlorinated organics (PCBs)*
Iron Unsaturated hydrocarbons
Manganese
Restrictive Waste Characteristics
The effectiveness of this treatment system may be affected by a number of
different waste characteristics. Some of these are:
o Presence of a wide range of contaminants may complicate the process
and produce unwanted side effects. For example, if oxidation of
organics is conducted in the presence of chromium (III), the
chromium will also be oxidized to the more toxic and mobile chromium
(VI).
o In situ soil treatment .may be affected by decreased permeability of
soils (due to hydroxide precipitation) or loss of adsorption
capacity (due to oxidation/reduction of soil organics).
o Aqueous wastes with high organic concentrations (higher than 100 ppm)
may require large volumes of oxidixing/reducing agents and costs may
escalate rapidly.
*Reduction or dichlorination of chlorinated organics is discussed in more
detail in Section 4.5
4-4
-------
Required Onsite Facilities/Capabilities
Site preparation, labor, and utilities requirements for a mobile system
include:
o Minimal site preparation. In many cases, properly graded access
roads are sufficient;
o Minimal labor because pH metering and reagent addition are
automatically controlled;
o Power for pumping, agitation and ozone generation (if ozone is
used);
o Water for slurrying of solid materials; and
o Dewatering and proper disposal of precipitated sludges from redox
treatment.
Environmental Impacts
The system is normally operated in a closed vessel; therefore no
significant air pollution impacts would be expected.
See Section 4.1 for a discussion of residuals treatment and disposal.
Costs
Costs for redox systems depend on the volume of waste treated, the
contaminants to be removed and the required reagents.
Andco Environmental Processes, Inc. offers a mobile unit for
electrochemical precipitation of heavy metals. The unit, with a capacity
of 50 gpm, rents for $300 to $350/day or can be purchased for about
$100,000 to $150,000 including solids separation or sludge dewatering.
Rexnord Inc. offers a mobile treatment system equipped with a multi-
component treatment train with capabilities for most of the physical/
chemical treatment process discussed in Chapters 4 and 5. The capacity of
this unit is 1 to 10 gpm, with total costs ranging from $0.07 to
$0.15/gallon for extended duration treatment of low to moderate strength
aqueous waste streams. Costs for short-term treatment may be considerably
higher.
Commercial Applications
Rexnord has incorporated chemical oxidation (hypochlorite) into its mobile
van (groundwater cleanup response system) for pilot-scale testing and
full-scale cleanups. The Rexnord system has a capacity of 1 to 10 gpm to
treat groundwaters with volatile organic compounds, extractable organic
compounds and heavy metals.
Andco Environmental Processes, Inc. has developed an electrochemical
process to remove heavy metals by adjusting the metal's valence state and
precipitating out the metal hydroxides. Over 150 fixed units have been
4-5
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installed around the country. The system precludes the use of chemical
additives for the precipitation step. A mobile unit is available which can
process up to 50 gpm of wastewater.
Envirochem Waste Management Services, Inc. and Chemical Waste Management,
Inc. also have mobile systems which can be used for redox processes as well
as neutralization, precipitation, phase separation, clarification and
carbon adsorption.
ATW Calweld offers a unique augering system that can inject and mix a
variety of detoxifying agents (oxidizers, neutralizers, fixatives) in the
subsurface based on simultaneous in situ monitoring of contaminants.
Ensotech, Inc. offers a mobile system for chemical redox, neutralization,
precipitation and immobilization. Capacities range from 20 to 120 gpm.
DETOX, Inc. also offers several chemical treatment processes in mobile
units.
Addresses and contacts for the above companies are listed in the appendix.
4-6
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4.3 NEUTRALIZATION
Process Description
Neutralization is the interaction of an acid (pH less than 5) or base (pH
greater than 9) with a solution with the pH of the resulting solution or
mixture between 5 and 9. Neutralization can'be used as a final waste
treatment process, or as a pretreatment process to prepare a waste stream
for further treatment. The process of neutralization is used in many
commercial applications and has a wide range of applicability to waste
treatment.
Neutralization can be performed using simple off-the-shelf equipment that
may easily be set up as a mobile system. The equipment for neutralization
usually consists of a chemical feed system and a rapid mixing process,
followed by another physical/chemical process for by-product removal as
appropriate. Many different equipment configurations are possible
depending on the specific waste material to be treated.
Sodium hydroxide, lime or sulfuric acid are the most common reagents added
to neutralize a waste. The quantity and concentration will depend on the
influent and desired effluent pH. The reaction products include water,
salts and solids that may precipitate. Figure 4.2 presents a typical
neutralization system.
Waste Types Handled
Neutralization is most often used on liquids, but also can be used on the
following wastes:
o Sludges, slurries and gases,
o Organic and inorganic waste streams, and
o Spent acid and alkali wastes.
Restrictive Waste Characteristics
Spent acid and alkali wastes with pH between 4.0 and 9.0 may not be
effectively treated by neutralization. The concentration of the waste will
determine the amount of neutralizing reagent required. Buffer capacity of
the waste will also affect the dosage requirements for neutralization. For
example, solids and sludges may require excessive dosages of chemicals due
to the difficulty of achieving complete mixing and the potentially high
buffer capacity of solid phases.
Required Onsite Facilities/Capabilities
Site preparation and utilities requirements for neutralization may include:
o A properly graded access road,
o Electric power for pumping and mixing of wastes, and
o A water source for preparation of neutralizing agents.
4-7
-------
pH CONTROLLER
u-a
LIME PUMP
WASTE ACID
TREATED EFFLUENT
(TO CLARIFIER IF NECESSARY)
NEUTRALIZATION TANK
pH CONTROLLER
TREATED EFFLUENT
(TO CLARIFIER IF NECESSARY)
NEUTRALIZATION TANK
pH CONTROLLER
TREATED EFFLUENT
(TO CLARIFIER IF NECESSARY)
ALKALI FEEDPUMP
NEUTRALIZATION TANK
FIGURE 4.2
SCHEMATIC DIAGRAM OF NEUTRALIZATION
4-8
-------
Environmental Impacts
The environmental concerns associated with neutralization include the
following:
o Toxic gases (e.g., ammonia, hydrogen sulfide and hydrogen cyanide)
may be released if wastes are not mixed slowly and are not properly
prepared.
o Neutralization may precipitate out heavy metals from solution and
result in significant quantities of sludge; sludge volumes produced
by neutralization of soils and sludges depend, on the waste
characteristics.
o Chemical complexes may not be effectively removed during further
processing.
o Additional processing of the sludges may be required in order to
meet applicable regulatory requirements for disposal.
Management of residuals from this treatment process are addressed briefly
in Section 4.1.
Costs
Capital costs reported for neutralization systems vary from $150,000 for a
3,000-gpd system up to $230,000 for a 22,000-gpd system with full
instrumentation. Operating costs are reported to vary from $0.07/gal for
3,000-gpd systems to $0.03/gal for 22,000-gpd systems (Superfund Treatment
Technologies - A Vendor Inventory, EPA, 1986).
Costs vary widely at all capacities depending upon:
o The degree of control required for the treatment process, and
o The availability of waste streams of appropriate acidity or
alkalinity to affect the neutralization without use of costly
chemicals.
In many cases, neutralization is a unit process in a larger treatment
system and the cost of neutralization is usually included in the system
cost.
Commercial Applications
Ecolochem, Inc. has incorporated neutralization (pH adjustment) into its
mobile water treatment plant for cleanups of up to 600 gpm. The Rexnord
system has a capacity of 1 to 10 gpm for groundwater treatment. The system
contains neutralization, clarification, air stripping, filtration, carbon
adsorption, reverse osmosis, ion exchange and sludge dewatering.
Enviro-Chem Waste Management Services, Inc. has a mobile system consisting
of neutralization, phase separation, heavy metal precipitation and carbon
filtration. The hydraulic capacity can range as high as 4,000 gpd.
Chemical Waste Management, Inc. has a mobile system capable of treating up
4-9
-------
to 100,000 gpd for metals removal. IT uses oxidation, precipitation,
neutralization and filtration processes. DETOX, Inc. offers custom systems
as mobile units. For information on company contacts, see the appendix to
this document.
4-10
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4.4 PRECIPITATION
Process Description
Precipitation, flocculation and sedimentation will be discussed as a single
process since they are commonly used together in waste treatment. They are
all fully developed processes and can be rapidly applied to a variety of
waste streams. Figure 4.3 shows a typical precipitation, flocculation and
sedimentation system configuration.
Precipitation is the physical/chemical process in which dissolved chemical
species in solution (e.g. metals) are transformed into solid phases for
removal. The chemical equilibrium relationships between the soluble
substances are generally altered by the addition of chemicals such as lime
and sodium sulfate. Additional chemicals may be needed to adjust the pH of
the mixture since the solubility of metal hydroxide and sulfides is very
dependent on pH.
Flocculation is a process in which small suspended particles are
transformed into larger settleable particles by the addition of chemicals.
Typically, the chemicals used for flocculation are alum, lime and
polyelectrolytes. The flocculating agents are first readily mixed to
disperse the agents; then the solution is slowly and gently mixed to allow
the formation of larger particles. As with precipitation, pH is an
important factor in controlling the chemical properties of the flocculating
agent. As a result, pH must be monitored.
Sedimentation is the process in which suspended particles in an aqueous
solution are allowed to settle under the process of gravity. The particles
settle in the bottom of the sedimentation tank. The sludge is then
collected and disposed of.
The equipment requirements for precipitation include:
o Reaction tank with a rapid mixer,
o Chemical storage tanks,
o Chemical feed pumps, and
o pH controls.
Additional equipment which may be required for the dewatering of the sludge
include clarifiers, filters and centrifuges.
Waste Types Handled
Precipitation is particularly well-suited for detoxifying aqueous solutions
containing heavy metals and suspended solids. It has been extensively used
to treat wastewaters contaminated with heavy metals. The heavy metals
include:
o Arsenic o Lead
o Cadmium o Manganese
o Chromium o Mercury
o Copper o Nickel
o Iron o Zinc
4-11
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PRECIPITATION
FLOCCULATION
CLARIFICATION
I
I'
ro
PRECIPITATING
CHEMICALS
FLOCCULATION AND
SEDIMENTATION AIDES
RAPID MIX TANK
o o
OUTLET
STREAM
CLARIFIER
SLUDGE
FIGURE 4.3
SCHEMATIC DIAGRAM OF CHEMICAL PRECIPITATION AND ASSOCIATED PROCESS STEPS
-------
Restrictive Waste Characteristics
Organic compounds may interfere with precipitation by forming organo-
metallic complexes. Cyanide and other ions may also complex with metals,
reducing the precipitation potential or requiring much higher
stoichiometric quantities of chemicals. Each metal salt has a different
optimum pH for maximum removal and precipitation.
Required Onsite Facilities/Capabilities
A properly graded access road will be necessary. Electric power will be
required for pumping, mixing, and sludge dewatering. Treated water may be
discharged on site or transported to a sewage treatment plant.
Environmental Impacts
Because sedimentation is a concentrating process, the resulting sludge may
require further treatment prior to disposal.
The water from the sludge dewatering phase may require further treatment
for organics removal before discharge to a receiving water or sewage
treatment plant.
Management of process residuals is discussed in Section 4.1.
Costs
The Andco system (described in Section 4.2) is used for electrochemical
precipitation of most metals. The unit, with a capacity of 50 gpm, rents
for $300 to $350 per day or can be purchased for about $100,000 to
$150,000, including solids separation and sludge dewatering.
Mobile wastewater treatment systems (see below) have been developed to
include neutralization, precipitation, sedimentation, filtration and carbon
adsorption. Costs for rental of these complete systems can range from
$5,000 to $25,000/month, depending on flow rate (Superfund Treatment
Technologies - A Vendor Inventory, EPA, 1986).
Commercial Applications
Rexnord, Ecolochem, Enviro-Chem, Chemical Waste Management, Inc., Ensotech,
DETOX and Tetra Recovery Systems all have complete mobile wastewater
treatment systems for cleanup. The Rexnord system has a capacity of 1 to
10 gpm for groundwater treatment. The system contains neutralization,
clarification, air stripping, filtration, carbon adsorption, reverse
osmosis, 'ion exchange and sludge dewatering. Enviro-Chem Waste Management
Services, Inc. has a mobile system consisting of neutralization, phase
separation, heavy metal precipitation and carbon filtration. The hydraulic
capacity is approximately 4,000 gpd. Chemical Waste Management, Inc. has a
mobile system for metals removal capable of treating up to 100,000 gpd. It
uses oxidation, neutralization, precipitation and filtration processes.
Ecolochem offers a system with up to 600 gpm treatment capacity. Contact
persons and addresses of the above companies are presented in the appendix.
4-13
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4.5 DECHLORINATION
Process Description
Dechlorination is a process in which chlorine is chemically removed from
chlorinated organic compounds such as PCBs and dioxins. At present, this
system is used primarily for dechlorination of transformer fluids. This
chemical treatment system usually employs a sodium-based reagent composed
of an alkali metal and polyethylene glycol (PEG). The mechanism for
dechlorination involves nucleophillic displacement of chlorine atoms by
PEG, to form an alkali metal chloride (typically KC1 or NaCl) and a
substituted organic polymer. By-products of this process include chloride
salts, polymers, and, occasionally, heavy metals.
The reagents are air- and water-sensitive. Therefore, the process should
take place in a nitrogen atmosphere. The process can tolerate very small
amounts of water (2000 ppm), but water content should be minimized. The
reagents react immediately with chlorinated hydrocarbons, inhibitors,
acids, thiols and chlorides.
A mobile dechlorination process for soils is currently under review by EPA.
The system for soil treatment would contain dewatering equipment, a heated
slurry reactor, and solid-liquid separation equipment.
Current mobile dechlorination units fit on a 40-foot tractor trailer. The
systems consist of the following:
o Reaction vessel,
o Mixing chambers,
o Reagent storage tanks,
o Chemical feed pumps,
o Dual filter beds, and
o Vacuum degasser.
A diagram of the dechlorination slurry process is provided in Figure 4.4.
Waste Types Handled
Commercially successful mobile operations have been limited to PCB-contami-
nated transformer fluids (organic fluids). However, efforts are being made
to apply this process to contaminated soils containing PCBs, dioxins and
other chlorinated hydrocarbons. Chlorinated acids and thiols have also
been dechlorinated by this process.
Restrictive Waste Characteristics
Moisture content adversely affects the rates of reaction and dewatering
should be a pretreatment step. Complete contact between the reagent and
the soil matrix is necessary for effective decontamination, so that both
reactants must be in the same phase (i.e., the soils must be in a slurry).
Contaminant concentration are also limiting. For example, PCB
concentrations exceeding 5,000 ppm can not be treated cost effectively due
to the excessive sodium requirements by this process.
4-14
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PCB
CONTAMINATED
SOIL
I
I»
en
REAGENT
REACTION
RECYCLE
I
WATER
REAGENT
RECOVERY
SOIL
WASHING
.CLEAN
SOIL
HEAT
WATER.REAOENT RESIDUAL
AND REACTION PRODUCTS
I
FIGURE 4.4
BLOCK DIAGRAM OF DECHLORINATION SLURRY PROCESS
-------
Required Onsite Facilities/Capabilities
A graded access road will be required. Electricity will be needed to set
up the process on site.
Environmental Impacts
The chloride salts and polymers that are by-products of the process are
insoluble in water and less toxic than the original contaminants. The
heavy metals may require treatment before disposal. Usually treated oils
containing less than 2 ppm of PCBs are considered PCB-free.
Costs
PCB dechlorination is significantly less expensive than incineration for
disposal of transformer fluids. At concentrations above 5,000 ppm, costs
are often comparable to those for incineration.
Commercial Applications
Currently, vendors treat only transformer oils of high purity. They have
not yet applied the system to soils.
Chemical Waste Management, Accurex, PPM Inc. and Sunohio have mobile
systems for PCB-contaminated oils utilizing a dechlorination process. The
systems have a capacity range of up to 10,000 gpd. This treatment is used
for oils with less than 10,000 ppm of PCBs and less than 2,000 ppm of
water.
Company addresses and contacts are listed in the appendix to this document.
4-16
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5.0 PHYSICAL TREATMENT TECHNOLOGIES
5.1 INTRODUCTION
This section describes the mobile physical treatment technologies used for
the cleanup of hazardous waste sites. In general, physical treatment
processes separate the waste stream by either applying physical forces or
changing the physical form of the waste. In both cases, the chemical
structure of the substances in the waste stream remains constant. The
advantages of these systems are that the processes are usually simple,
relatively inexpensive, and can be applied to a wide range of wastes.
Physical treatment technologies discussed in this section are listed and
briefly described below.
o Air Stripping - a system that provides for mass transfer of organic
contaminants from a liquid phase to a gas phase.
o Mechanical Aeration/Extraction - the process of extracting volatile
contaminants from soil using aeration, often augmented with heating
of soil.
o Steam Stripping - the use of steam for the volatilization of organic
species.
o Distillation - a process that separates components of a liquid
mixture by partially vaporizing the mixture.
o Activated Carbon Adsorption - the process of collecting soluble
substances on the surface of activated carbon by surface attraction
phenomena.
o Evaporation - a process where heat energy is applied to a solution,
slurry or suspended solids mixture to vaporize part of the mixture
while concentrating the semi-solid component.
o Soil Flushing/Soil Washing - the process of extracting contaminants
from soil using washing fluids.
o Filtration - the removal of suspended solids from a fluid by passage
through a porous media.
o Ion Exchange - the process of exchanging toxic ions in solution for
a non-toxic ion from a solid resin.
o Membrane Separation - the use of specifically constructed membranes
to selectively reject contaminants.
o Phase Separation - application of force to remove toxic components
with a specific gravity different from water.
5-1
-------
As discussed under many of the other treatment technologies, physical
treatment processes will also produce residuals that must be disposed of in
an environmentally safe manner. Treatment sludges may require additional
treatment either on site or off site prior to disposal. Treatment needed
may include dewatering (and subsequent treatment of vastewater) and
immobilization.
The further treatment required for concentrated solids and sludges will
depend on the type and level of contamination. A number of thermal,
physical, chemical, and immobilization processes may be used as treatment
alternatives. Liquids will also require further treatment if hazardous
constituents, such as volatile organics, are present.
5-2
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5.2 AIR STRIPPING
Process Description
Air stripping consists of a contacting system that provides for mass
transfer of volatile organic contaminants from a dilute aqueous waste stream
into an air stream. Air stripping is typically applied to groundwater or
wastewater contaminated at low levels with volatile organics. An air
stripping unit can be designed in a number of configurations to optimize
air-water contact. The different types of air stripping units include:
o Countercurrent packed and tray towers
o Diffused aeration water cascades
The removal efficiencies of organic compounds in an air stripping unit can
be predicted to some extent by Henry's Law constant (an equilibrium distri-
bution coefficient of the individual organic's concentrations between the
air and liquid or solid phases). A higher value of Henry's Law constant
indicates a higher affinity of the organic compound for the air phase.
Packed towers with air-to-liquid ratios in excess of 150 to one (volume
basis) can achieve up to 99.9 percent removal of some volatile compounds
from aqueous wastes while the other aeration devices have removal efficien-
cies between 50 and 90 percent. The system selected will depend on the
physical/chemical characteristics of the waste stream and the required
removal efficiency. Figure 5.1 depicts a mobile packed tower air stripper.
A packed tower constructed out of fiber reinforced plastic (FRP) is well
suited as a mobile system. FRP towers are structurally sound and
lightweight, making them easy to transport. Loose or structured packing of
trays can be used. However, loose packing may settle during transport.
Therefore, loose packing is usually loaded into the column on site.
A modification of the stripping process is being applied to contaminated
soils (Section 5.3). The process is similar to air stripping but instead
of forcing air through a packed tower medium, a vacuum is applied to pull
air through the soil.
Waste Type Handled
Air stripping may be used to remove volatile organic compounds (Henry's
Constant >3.0 X 10" atm-m /mole) from aqueous wastes. Heating the
influent waste stream will result in removal of less volatile organics such
as ketones. In general, organic concentrations less than 1.0 percent are
treatable by air stripping.
Restrictive Waste Characteristics
Air stripping is not appropriate for the removal of the following substances:
o Low volatility compounds,
o Highly soluble compounds,
o Metals, or
o Inorganics
5-3
-------
\
en
i
-Pi
\
.. ~T^L I
FIGURE 5.1
PACKED COLUMN AIR STRIPPER : SCHEMATIC DIAGRAM OF
DESIGN BASIS, SIDE, TOP, AND ON ROAD VIEWS
-------
Aqueous waste streams with high suspended solids concentrations, elevated
levels of iron, manganese or carbonate may reduce packing efficiency due to
precipitation and channeling.
Required Onsite Facilities/Capabilities
Equipment needs include:
o Pumps,
o Air blowers,
o Storage tanks, and
o Air pollution controls.
Environmental Impacts
The following environmental concerns are associated with air stripping:
o Air stripping produces air emissions of volatile organic compounds.
These emissions can be treated by capturing them using vapor phase
carbon adsorption or destroying them in a fume incinerator.
Estimates of stack emissions may be required as well as dispersion
modeling of emissions to determine if air emission control is
necessary.
o The treated wastewater from this process may require further
treatment for removal of metals and non-volatile organics.
o Periodic cleaning of packed towers may result in small quantities of
metal (e.g., iron) sludge, which will require disposal.
o Dehumidification prior to vapor phase controls may result in a
concentrated waste stream.
Residuals management is briefly discussed in Section 5.1.
Costs
Capital costs for packed tower air strippers are relatively low compared to
other treatment techniques. A 700 gpm unit may cost from $150,000 to
$350,000, without vapor phase controls. Air pollution controls will
roughly double the costs.
Commercial Applications
Several manufacturing companies supply mobile packed tower air strippers
for rent and/or purchase. A partial list is provided below:
o Hydro Group,
o OH Materials,
o Haztech,
o Carbon Air Services,
o Detox Inc.,
o IT Corp.,
o Oil Recovery Systems Inc.,
5-5
-------
o ESE,
o Kipin Industries Inc.,
o Resource Conservation Co.,
o Terra Vac Inc.
Addresses and names of contacts are found in the appendix.
5-6
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5.3 MECHANICAL AERATION/EXTRACTION
Process Description
Mechanical aeration or extraction entails contacting clean air with the
contaminated soils in order to transfer the volatile organics from the soil
into the air stream. Note that this treatment does not remove non-volatile
organics. Subsequent treatment of this air stream can be accomplished
through the use of activated carbon cannisters and/or water scrubbers or
incineration of volatile emissions in an afterburner. A number of
different methods have been employed for this process, including:
o mechanical rototilling,
o enclosed mechanical aeration systems,
o pneumatic conveyor systems,
o low temperature thermal stripping system, and
o in situ vacuum extraction systems.
Mechanical rototilling is no longer considered an acceptable alternative
due to uncontrolled air emissions of volatile organics.
Enclosed mechanical aeration systems consist of mixing the contaminated
soils in a pug mill or rotary drum system. The volatile organics are
released from the soil matrix by the churning action (air/soil contact).
Induced air flow within the chamber captures the volatile organic emissions
and passes them through an air pollution control device, i.e., water
scrubber or vapor phase carbon adsorption system. The air emissions would
then be discharged through a properly sized stack.
Pneumatic conveyor systems consist of a long tube or duct carrying air at
high velocity, an induced draft fan to propel the air, a suitable feeder
for addition and dispersion of particulate solids into the air stream, and
a cyclone collector or other separation equipment for final recovery of the
solids from the gas stream. Several units of this type heat the inlet air
up to 300°F to induce volatilization of the organic contaminants. The
typical air velocity calculated at the air exit is 75 cubic feet per
second. This method allows for high air to solids ratios which can be
applied for effective contaminant removal (similar to air to water ratios
in packed tower air strippers). Pneumatic conveyors are primarily used in
the manufacturing industry for drying of solids with up to 90% (wet basis)
initial moisture content.
Low temperature thermal stripping systems (Figure 5.2) consist of a similar
configuration as the enclosed mechanical aeration except that additional
heat transfer surfaces may be added for soil heating. Induced air flow
conveys the desorbed volatile organic/air mixture through a combustion
afterburner for the destruction of the organics. The air stream is then
discharged through a properly sized stack.
Vacuum extraction systems consist of a high volume vacuum pump connected
via a pipe system to a network of boreholes or wells drilled in the
contaminated soil zone. Excavation is not required for this system. The
vacuum pulls air through the contaminated soils, stripping volatile
organics, and the air is subsequently fed through a condenser to recover
5-7
-------
AIR TO
ATMOSPHERE
HOT OIL
RESERVOIR
AIR CONTAINING
STRIPPED VOC'S
in
CD
COMBUSTION AIR
BLOWER
AIR
AIR
PREHEATER
SOURCE: U.S. ARMY TOXIC AND
HAZARDOUS MATERIALS AGENCY
ABERDEEN PROVING GROUND, MD
NOVEMBER, 1985
21010
FIGURE 5.2
SCHEMATIC DIAGRAM OF LOW TEMPERATURE THERMAL STRIPPER
-------
free product, and/or through an emissions control systems, i.e. a water
scrubber or vapor phase carbon adsorption system. The system can also
serve as. a monitoring system for leaks from sources such as underground
storage tanks, and can recover substantial volumes of leaked chemical
products.
The systems described above have been developed in the last few years in
response to soil contamination problems. These systems have several
advantages including:
o considerably lower cost for leasing and operation than mobile
incineration systems,
o achievement of volatile contaminant removal criteria, and
o replacement of treated soil in the original excavation, or in the
case of vacuum extraction, no excavation
Waste Types Handled
Aeration/extraction may be used to strip^volatile organic compounds
(Henry's Law Constant > 3.0 x 10 atm-m /mole) from soils or similar
solids. This would include:
o benzenes, toluenes, xylenes,
o TCE and other volatile solvents,
o ketones, alcohols.
Heating the soils during the aeration process will result in accelerated
rates of stripping of highly volatile compounds and enhanced removal of
less volatile organics, and can produce removal effeciencies greater than
99.99%. Aeration/extraction can handle elevated levels of volatiles
organics in soils. Low temperature (50 C to 150 C) thermal stripping
systems have handled up to 22,000 ppm total VOC with 99.99% removal
efficiency.*
Vacuum extraction processes can be used to remove insoluble free
contaminant from the top of a water table. Air pollution control systems
may not handle highly concentrated emissions effectively. Afterburner
incinerations systems may be appropriate for these situations.
Restrictive Waste Characteristics
Aeration/extraction is not effective for the following:
o low volatility organics,
o high solubility compounds,
o metals, or
o inorganics.
*U.S. Army Toxic and Hazardous Materials Agency
5-9
-------
Required Onsite Facilities/Capabilities
Site preparation and utility requirements include:
o a properly graded access road
o electric power
o graded staging area
Emissions monitoring stations may be required on site perimeters to monitor
for uncontrolled releases of organics.
Environmental Impacts
The following environmental concerns are associated with aeration/extraction:
o Air stripping produces air emissions of volatile organic compounds.
These emissions can be treated by capturing them using vapor phase
carbon adsorption or destroying them in a fume incinerator.
Estimates of stack emissions may be required as well as dispersion
modeling of emissions to determine if air emission control is
necessary.
o The scrubber effluent from the air pollution control process process
may require further treatment to remove metals and non-volatile
organics.
o The treated soils may require additional treatment for non-volatile
organics.
Residuals management is briefly discussed in Section 5.1.
Costs
Data on costs is not yet available from the demonstrations done using low
temperature thermal stripping units.
Costs for vacuum extraction tend to be highly dependent on the volume of
soil to be treated. Treatment costs are generally a small fraction of
costs for systems using excavation (Terra Vac., 1986). Smaller volumes may
be one to two orders of magnitude more expensive per yard due to the
initial expense of well installation and monitoring.
Commercial Applications
American Toxic Disposal, Inc. and Kipin Industries, Inc. offer a mobile
thermal processing system for treatment of soils contaminated with a wide
range of organics. Temperatures and solid residence times can be increased
for removal of non-volatile organics. Roy F. Weston, Inc. performed a
demonstration of low temperature thermal stripping for the U.S. Army Toxic
and Hazardous Materials Agency. Terra Vac of Puerto Rico offers complete
vacuum extraction cleanups of soils contaminated with organics. The system
reportedly works well for leaking underground storage tanks.
Company contacts and addresses are listed in the appendix.
5-10
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5.4 STEAM STRIPPING
Process Description
Steam stripping is a unit process that uses steam to extract organic
contaminants from a liquid or slurry. Direct injection of steam and
multiple pass heat exchangers are the two most prevalent methods of steam
stripping. Steam stripping by direct injection of steam can be used to
treat aqueous and mixed wastes containing organic contaminants at higher
concentrations and/or having lower volatility than those streams which can
be stripped by air. It is an energy-intensive process and the steam may
account for a major portion of the operating costs. A schematic diagram is
presented in Figure 5.3.
This process is similar to steam distillation except that reflux of the
stripped and recovered material does not usually occur. The proccess can
handle a higher concentration of solids in the waste stream than a
distillation unit due to the increased heat transfer surface area of the
steam stripping unit. Wastes of more variable composition can also be
processed more effectively by steam stripping than by distillation. One
disadvantages of this process is the increased concentration of the removed
volatiles. The concentrated removed volatiles will require further
treatment (i.e., distillation) before reuse, or destruction by
incineration.
Waste Type Handled
Steam stripping is a widely used process. The following is a list of wastes
that can be removed with steam stripping from aqueous solutions and solids:
o Volatile organics,
o Phenols,
o Ketones, and
o Phthalates.
Water miscible organics and metal contaminants are not removable by this
process.
Restrictive Waste Characteristics
In general, steam stripping is effective in the removal of high
concentrations of organics ranging from 1 to 20 percent.
Solids or slurries of high solids content cannot be treated by steam
stripping because contact between steam and solid materials is too
difficult to achieve.
Required Onsite Facilities/Capabilities
Energy requirements are the primary limitations on the equipment sizing and
removal effectiveness. Additional equipment required on site are:
o Air and water condensers,
o Electric or diesel boilers,
5-11
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FEED
BATCH
STILL
CONDENSER
PARTIAL RECYCLE
STEAM
CONDENSATE
BOTTOM
PRODUCT
ACCUMULATOR
DISTILLATE
DISTILLATION
COLUMN
VOLATILE
LIQUIDS)
PERFORATED TRAY TYPE
DISTILLATION PLATE
ACCUMULATOR
DISTILLATE
STEAM
CONDENSATE
SOURCE: ADL. 1977
STILL BOTTOMS
(RESIDUE)
FIGURE 5.3
SCHEMATIC DIAGRAM OF BATCH AND CONTINUOUS DISTILLATION
5-12
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o Storage equipment, and
o System for residue removal.
Residuals management is discussed in Section 5.1.
Environmental Impacts
The following environmental concerns are associated with air stripping:
o Steam stripping produces air emissions of volatile organic
compounds. These emissions can be treated by capturing them using
vapor phase carbon adsorption or destroying them in a fume
incinerator. Estimates of stack emissions may be required as well
as dispersion modeling of emissions to determine if air emission
control is necessary.
o The treated wastewater from this process may require further
treatment to remove metals and non-volatile organics.
o Periodic cleaning of packed towers may result in small quantities of
metal (e.g., iron) sludge, which will require disposal.
o Dehumidification prior to vapor phase controls may result in a
concentrated waste stream.
Residuals management is briefly discussed in Section 5.1.
Costs
Costs for a portable steam stripping system are not available. However,
typical costs for a permanently constructed steam stripping system are
available. A system to handle 25,000 gpd would cost $400,000 for capital
expenditures and $130,000 (or $0.17 per gallon) in annual operation and
maintenance costs. Costs are in 1985 dollars (Jacobs Engineering, 1986).
Commercial Applications
Although steam stripping is widely used in industries such as organic
chemical manufacturing, no mobile steam stripping units have been applied
to hazardous waste treatment. A number of companies have, however,
expressed interest in developing a mobile unit. Several petroleum
companies may also be developing mobile systems.
5-13
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5.5 DISTILLATION
Process Description
Distillation is a unit process that separates components of a liquid or
sludge mixture by partially vaporizing the mixture and separately
recovering the vapors and residue. The more'volatile components of the
original mixture concentrate in the vapor (distillate) while the less
volatile, semi-solid components concentrate in the residue (bottoms). This
process can be used for separating mixtures of organic liquids into light
and heavy fractions. The light fraction can be recycled or used as a
boiler fuel. The heavy fraction usually requires further processing or can
be burned in a hazardous waste incinerator.
There are two principal methods by which distillation may be carried out.
The first method boils the mixture to produce a vapor phase and a liquid
phase which are then separated. The second method returns a fraction of
condensate to the unit so that the condensate has contact with the rising
vapors. Both methods may be used on a continuous or batch process. The
batch process is used primarily for more viscous fluids.
However, given the wide compositional fluctuations in characteristics of
CERCLA wastes, the utility of mobile distillation units is very limited.
This is due to difficulties in adopting a sophisticated feed-sensitive
process to a highly variable waste stream.
Schematic diagrams for batch and continuous distillation are illustrated in
Figure 5.4.
Waste Type Handled
Distillation is very useful for reclaiming spent solvents from industrial
processes, such as the metal finishing industries, or purifying certain
aqueous, such as those heavily contaminated with organics (10,000 ppm).
The following is a list of some reclaimable solvents:
o Acetone,
o Alcohol,
o Chlorinated organics,
o Hydrocarbons, and
o Ketones.
Restrictive Waste Characteristics
Fractional distillation is not suited for the following waste streams:
o Liquids with high viscosity at high temperature,
o Liquids with a high solids concentration,
o Polyurethanes, and
o Inorganics.
5-14
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FEED
BATCH
STILL
CONDENSER
PARTIAL RECYCLE
- STEAM
CONDENSATE
BOTTOM
PMOIJUCT
ACCUMULATOR
DISTILLATE
DISTILLATION
COlUMN
PERFORATED TRAY TYPE
DISTILLATION PLATE
ACCUMULATOR
DISTILLATE
STEAM
CONDENSATE
SOURCE: ADL. 1977
STILL BOTTOMS
IHESIUUEI
FIGURE 5.4
SCHEMATIC DIAGRAM OF BATCH AND CONTINUOUS DISTILLATION
5-15
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Required Onsite Facilities/Capabilities
Energy requirements are the primary limitations on the equipment sizing and
removal effectiveness. Additional equipment that may be required on site
includes:
o Air and water condensers,
o Electric or diesel powered reboiler,
o Storage tanks, and
o System for residue removal.
Environmental Impact
Distillation results in two concentrated streamsthe recovered solvent and
still bottoms. The still bottoms can be incinerated or used as a boiler
fuel. Metal cleaning solvents that are reclaimed by this process result in
a sludge residual that may contain high concentrations of metals. Since
the recovered solvents have been volatilized, incidental air emissions may
become a problem.
Residuals management is briefly discussed in Section 5.1.
Costs
Costs for portable distillation systems are not available. However, a
permanently constructed distillation system designed to handle 50 gal per
hour requires an annual operation and maintenance budget of approximately
$610,000 or $1.70/gal in 1985 dollars. The capital construction cost for
such a plant in 1985 dollars would be $200,000 (Jacobs Engineering, 1986).
Commercial Application
Currently, only Mobile Solvent Reclaimers, Inc. of St. Joseph, Missouri, is
producing a mobile distillation unit. The unit has a minimum capacity of
100 gal with a maximum throughout of 500 gal per day. The average
throughput is 40 gal per hour. The company address and point of contact
are given in the appendix.
5-16
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5.6 ACTIVATED CARBON ADSORPTION
Process Description
The activated carbon adsorption process is one of the most frequently
applied technologies for the removal of trace organic compounds from an
aqueous solution. Adsorption is a surface phenomenon in which soluble
molecules from a solution are bonded onto a particular substrate.
Therefore, one of the most desirable properties of an adsorbent is a high
surface to volume ratio. Activated carbon (with a surface to volume ratio
ranging from 500 to 1400 m /g) is a good adsorbent for effective removal of
organic compounds.
Activated carbon will adsorb most organic compounds to some degree.
Factors that affect the adsorption process include:
o Carbon pore structure,
o Carbon contact time,
o Temperature, and
o pH.
Mixtures of organics may cause significantly reduced adsorption capacity
for certain compounds due to the preferential adsorption of other compounds
by the carbon. Competitive adsorption of organic compounds is extremely
complicated and difficult to predict. Therefore, it is recommended that
pilot treatability tests be performed on the waste in question.
A typical activated carbon adsorption system is shown in Figure 5.5.
Gravity flow and multicolumns in series are the most commonly designed
contacting systems.
Waste Type Handled
Carbon adsorption can be applied to aqueous and gaseous wastes containing a
wide range of organic compounds. The following is a list of compounds
that can be successfully removed from waste streams:
o Organic liquids with metals and halogens,
o Organic nitrogen compounds,
o Chelated heavy metals, and
o Volatile organics.
Restrictive Waste Characteristics
The effectiveness of activated carbon adsorption is limited by the
following waste characteristics:
o Low molecular weights,
o High polarities, and
o High solubility.
5-17
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CARBON MAKE-UP
en
I
00
TO CARBON
REGENERATION
SYSTEM
INFLUENT
WATER
O
H
CARBON BED
HIGH PRESSURE SPENT CARBON SLURRY
WATER
FROM CARBON
REGENERATION
SYSTEM
CARBON BED
^EFFLUENT
(TREATED WATER)
FIGURE 5.5
SCHEMATIC DIAGRAM OF GRANULAR ACTIVATED CARBON COLUMNS
POM Pn«*tr»n
-------
The following is a list of applications for which the activated carbon
adsorption process is not recommended:
o High solids content (greater than 500 mg/1),
o Unassociated metals, and
o High humidity gas streams.
Required Onsite Facilities/Capabilities
Carbon contacting beds can be skid-mounted and placed on flat bed trucks or
railcars for transport to various sites.
Additional equipment that may be required includes:
o Pumps and piping,
o Backwash equipment,
o Carbon transfer equipment, and
o A carbon regeneration system (if cost-effective).
Environmental Impacts
The exhausted carbon will contain all of the waste constituents removed
from the waste streams. The carbon must be either regenerated (on or off
site) or disposed of in a secure landfill (carbon with PCBs or dioxin are
not currently regenerated by the vendors). Thermal regeneration of the
used carbon is the most common method currently used. Other methods of
regeneration employed are solvent and steam regeneration.
Periodic backwashing of the carbon will require holding tanks for the
backwash. Often the backwash is allowed to settle and the liquid portion
is sent back through the carbon. The small amount of sludge generated
during settling contains high concentration of organics and requires
disposal.
Costs
The capital cost for a 20,000 gpd carbon contact system will be
approximately $200,000. The carbon will cost approximately $.75 per pound.
The carbon usage rate will vary greatly depending on the concentration of
the adsorbate in the wastewater. Typically, usage rates will vary between
1 and 7 pounds of carbon per 1000 gallon/wastewater treated. Total cost
will be approximately one to two cents per gallon of wastewater treated.
However, it should be noted that total operating costs are heavily
dependent on the carbon usage rate as carbon replacement is the largest
cost factor (Calgon Carbon Corp., 1986).
Commercial Applications
The EPA has a mobile emergency environmental response unit (the "Blue
Magoo") that contains three sand filters followed by three granular
activated carbon columns in series. The system has operated at over 20
different sites. Many commercial service companies, as well as vendors,
supply mobile carbon adsorption systems. Calgon Carbon Corp. has mobile
units which vary in size from 2,000-40,000 pounds of carbon. The capacity
5-19
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of these units can range from 10 to 600 gpm. Vendors who also have
mobile treatment systems which include an activated carbon adsorption
process are Rexnord, Inc., Chemical Waste Management, Inc., and Enviro-Chem
Waste Management Service. The capacity of the available units range from
1,000-10,000 gpd. Currently there are no commercial mobile regeneration
units available. A partial list of suppliers for carbon adsorption systems
is presented in the appendix.
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5.7 EVAPORATION/DEWATERING
Process Description
Evaporation is a unit process in which heat energy is applied to a liquid
solution, slurry or suspended solids mixture in order to vaporize the more
volatile components of the mixture. This results in a concentrated solid
or semi-solid which can subsequently be handled and treated more
effectively. The vapor stream is either condensed and collected or
released into the atmosphere, depending upon the specific evaporation
process and the volatilized components. Therefore, the primary use of
evaporation is as a pre-processing step for concentrating or removing
contaminants of concern.
Evaporation processes include both conventional and unconventional
technologies. Individual technologies are listed below and discussed in
the following paragraphs.
Unconventional Technologies
Carver-Greenfield process
Conventional Technologies
Thin film evaporation
Kettle evaporation
Tubular evaporation
Scraped surface evaporation
Solar evaporation
The most common conventional evaporation process used in the waste
recycling industry today is agitated thin-film evaporation. Thin-film or
wiped-film evaporators are widely used to thicken viscous liquids and
slurries. Higher solids content wastes are particularly suited for
thin-film evaporation. A thin-film system consists basically of a large
diameter heating surface on which a thin film of material is continuously
wiped (Figure 5.6). The volatile portion is vaporized, leaving
concentrated semi-solids.
Other types of conventional evaporation processes include kettle, tubular,
scraped surface and solar evaporators. Solar evaporation is widely
practiced in arid climates. Wastewater or liquid wastes are placed in
lined lagoons and evaporated by solar energy leaving concentrated solids
behind.
An unconventional evaporation technology with hazardous waste applications
is the Carver-Greenfield process. This process involves the addition of
oil to the waste stream as a fluidizing medium to maintain liquid phase
fluidity as the solids content increases. The oil is subsequently
reclaimed by centrifugation and recycled.
Waste Type Handled
Evaporation can be applied as a pre-processing step or treatment process
for liquids, slurries or suspended solids mixtures. Specific waste streams
that may be treated by this process include:
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IXHAUST <
VACUUM
DISTILLED VAPOR
JCOOL'NG (WATER
MEAT
EXCHANGER
CONDENSATE
(TEAUCCMDENSATE
[VAPOR
CMAICER
(7
mo
OlLUTE LIQUID
CONCENTRATED LIQUID
EXHAUST
TRANSFER
»UMP
TYPICAL SINGLE EFFECT EVAPORATOR - FALLING FILM TYPE
TYPICAL MULTl-EFFECT (TRIPLE EFFECT) EVAPORATOR - FALLING FlLMTYPE
FIGURE 5.6
SCHEMATIC DIAGRAM OF SINGLE AND MULTIPLE
EFFECT EVAPORATORS
5-22
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o Concentrated liquid solutions,
o Highly viscous liquids,
o Slurries,
o Organic or metal sludges, and
o Soils contaminated with volatiles.
Low boiling point components will vaporize from mixtures more easily than
other components.
Wastes that may not be suitable for treatment via this process include
finely divided solids which, while improving heat transfer, may be
entrained in vapor. Organic materials that cause foaming and entrainment
are also restricted from treatment via evaporation/dewatering.
Restrictive Waste Characteristics
Waste characteristics must be carefully analyzed for suitability. Special
consideration must be given to waste characteristics that result in crystal
formation, scaling, abrasion and/or corrosion.
Environmental Impacts
Two process streams are generated by evaporation processes a
concentrated solid or semi-solid and a vapor component. Both components
generally require further treatment as discussed in Section 5.1. Vaporized
liquids will also require further treatment if hazardous constituents such
as volatile organics are present. If the liquid being evaporated is water,
there is generally little potential for hazardous air emissions from the
resulting vapor.
Costs
The costs for a mobile evaporation/dewatering system are not currently
available. However, typical cost for a permanently constructed
evaporation/dewatering system are available. A system to handle 50,000 gpd
will have a capital cost of $145,000 with an annual operation and
maintenance budget of $150,000 (Jacobs Engineering, 1986).
Commercial Applications
Evaporation processes are widely used in industrial and hazardous waste
application. However, they are primarily fixed or stationary processes.
Two companies offering mobile evaporation processes are Kipin Industries,
Inc. and Resource Conservation Company. Company contacts and addresses are
listed in the appendix.
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5.8 SOIL FLUSHING/SOIL WASHING
Process Description
These processes extract contaminants from a sludge-soil matrix using a
liquid medium as the washing solution. This washing solution is then
treated for removal of the contaminants via a conventional wastewater
treatment system. Soil washing can be used on sludge and excavated soils
fed into a contactor or washing unit. A similar process known as soil
flushing can be applied on unexcavated soils (in situ) using an
injection/recirculation system.
Washing fluids may be composed of the following:
o Water,
o Organic solvents,
o Water/chelating agents,
o Water/surfactants, and
o Acids or bases.
After the contaminants have been removed from the washing fluid, the fluid
may be recycled through the soil washing unit. In the case of in situ soil
flushing, the treated washing solution may be reinjected into the soil via
a recirculation system. Soils may require multiple washing/flushing cycles
for effective contaminant removal. Only certain types of soils may be
washed and the soil must be uniform.
Soil washing systems. Tank treatment systems using excavated soils can
have certain advantages:
o Close process control can provide more effective contaminant
removal, as disaggregation of soils improves soil water contact,
o Use of strong additives or washing fluids such as solvents is
simplified due to the elimination of the risk of uncontrolled
groundwater contamination and environmental degradation, and
o Smaller volumes of washing fluid are required and fluid recycling
improved.
Soil flushing systems. These systems can be used very effectively in
conjunction with mobile groundwater treatment systems. Pump and treatment
systems for groundwater can be combined with injection of washing fluids
upgradient of the extraction wells to produce accelerated flushing and
decontamination of soils and groundwater in situ. The treated groundwater
can be reinjected as a washing fluid, creating a closed loop recirculation
system. ' Combined groundwater/soil flushing systems can eliminate the costs
of removing contaminated soils off site and reduce the cost of separate
soil washing and groundwater treatment systems.
Treatment of washing fluids. The leachate collected from the soil
contacting process can be recycled by selecting a treatment process for the
particular contaminants, e.g., air stripping of water for VOC removal. The
separation of the extracted contaminants from the washing fluid can be
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accomplished by conventional treatment systems suited to the particular
contaminants. Problems have arisen with the use of water/surfactant
systems because a leachate treatment system has not yet been developed to
selectively remove contaminants and pass the surfactants through intact.
Waste Type Handled
Depending on the type of washing fluid additives used for the enhancement
of contaminant removal, waste types that can be removed using soil
washing/flushing include the following:
o Heavy metals (e.g., lead, copper, zinc),
o Halogenated solvents (e.g., TCE, trichloroethane),
o Aromatics (e.g., benzene, toluene, cresol, phenol),
o Gasoline and fuel oils, and
o PCBs and chlorinated phenols.
Removal of each waste type is enhanced through addition of the following
compounds:
Waste Type Compound
Metals: Cations Weak acids, reducing agents, or chelating
agents (ethylene diamine tetracetic acid
and citric acid)
Anions (arsenic, selenium) Water with oxidizers (H202)
Organics (insoluble) Organic solvents (alcohols, alkanes) or
water with surfactants
Organics (soluble) Water only, or water with surfactants
Desirable washing fluid characteristics for soil washing are listed below:
o Favorable separation coefficient for extraction,
o Low volatility,
o Low toxicity,
o Safety and ease of handling,
o Recoverability, and
o Treatability of washing fluid.
The areal distribution of waste types is very important in determining the
effectiveness of this process. Variability of waste types can make
formulation of suitable washing fluids difficult. Some contaminants may be
removed effectively while others are not (e.g., solvents and metals may be
difficult to remove simultaneously).
Restrictive Waste/Site Characteristics
In situ flushing systems have limitations due to the lack of close process
control in the subsurface. Critical site factors include the following:
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o Soil characteristics
- highly variable soil conditions can produce inconsistent flushing
- high organic content can inhibit desorption of the contaminants
- low permeability (high silt or clay content) reduces percolation
and leaching
- chemical reactions with soil, cation exchange and pH effects may
decrease contaminant mobility
o Site hydrology
- groundwater flow must be well-defined, permitting recapture of
soil washing fluids.
These systems have experienced some problems related to solid/liquid
separation subsequent to the washing phase. This is often due to the high
percentage of silt or clay in the soil material. This important unit
operation should be considered when evaluating the applicability of this
process to a site.
Whether in situ or excavation systems are utilized, laboratory and pilot
testing will be necessary to determine feasibility. Contaminant removal
rates may not be adequate to reduce soil contamination below required
action levels.
Required Onsite Facilities/Capabilities
All systems employing this process are mobile and are set up at the
contamination site, as transportation costs for moving the soil would make
this system uneconomical. Soil flushing is the most common application and
is often utilized in conjunction with a contaminated groundwater treatment
system. The groundwater is pumped out through extraction wells, treated
and reinjected upgradient (sprayed above soils if in the unsaturated zone)
and leached through the contaminated soil. The leachate is then
recollected through the extraction wells, treated and reinjected back into
the system, providing for a closed loop system.
The soil washing process includes soil washing systems such as
countercurrent extraction equipment, a pug mill, or a truck-loaded cement
mixer. A soil washing system treating excavated contaminated soils can
provide a more effective removal process through better soil-water contact
and enable less water volume to be used for an equivalent waste removal
process.
Environmental Impacts
As with other mobile systems, residues and unrecyclable washing fluid may
require further treatment and disposal off site. Effluent from mobile soil
washing systems may require further treatment before final discharge to
municipal sewer systems or offsite drainage systems, as discussed in
Section 5.1.
With soil flushing systems, potential does exist for generating some soil
and groundwater contamination from the washing fluid itself. Use of
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biodegradable additives in the washing fluid may prevent contamination of
the soil and groundwater by the washing fluid.
Costs
Several systems have been employed at hazardous waste sites, however none
have been sufficiently developed to estimate-costs. A soil washing system
that is being tested at Lee's Farm, Wisconsin has an estimated cost of
about $150-$200/yd excluding development costs. The major cost of the
project is usually associated with the washing fluid treatment system.
Commercial Applications
Currently, several hazardous waste sites throughout the country are
employing or plan to employ this technique for the cleanup of contaminated
soils. Some have reached more developed stages than others but all have
had to test this system on the site-specific conditions of concern.
A list of sites where this technology has been used includes the following:
- Volk Air National Guard Base, Juneau County, Wisconsin. Performed by
the Air Force Engineering and Service Center, Tyndall AFB, FL
32403-6001. Soils contaminated with volatile organics were leached with
water/2% surfactant and the leachate was regenerated by air stripping.
- Lee's Farm Wisconsin - Battery Manufacturing. Lead-contaminated soils
were leached with water/5% EDTA and the leachate was regenerated by
electrolysis. Contact Charlie Castle, on-scene coordinator in EPA
Region v". (312) 535-2318.
- Celtor Chemical Works, Hoopa Indian Reservation - Ore Enrichment Plant:
Tailings which include cadmium, copper and zinc. Contact Nick Morgan,
project manager for EPA Region IX. (916) 243-5831.
- Battery Dumping Pit - Leeds, Alabama. Lead contaminated soils were
leached with a water/2% EDTA solution and the leachate was regenerated
by sulfide precipitation. Contact Richard Travers, EPA Emergency
Response Team. (201) 321-6677.
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5.9 FILTRATION
Process Description
Filtration may be used for two primary purposes:
o Removal of suspended solids from a fluid by passage of the fluid
through a bed of granular material, and
o Dewatering of sludges and soils by vacuum, high pressure or gravity.
Granular media filters (typically sand and anthracite) remove
suspended solids through straining, physical adsorption and
coagulation-flocculation. These filters may be pressurized or
gravity-fed with loading rates ranging from 2 to 15 gpm/sq ft.
Various filtration methods have been employed to dewater sludges. They
include:
o Vacuum filtration,
o Belt filter press, and
o Chamber pressure filtration.
Vacuum filtration typically is a mechanically supported cylindrical
rotating drum covered by a filter medium (cloth, coil springs or wire mesh
fabric). Water is drawn into the center vacuum while the solids are
scrapped off the drum.
The belt filter press continuously squeezes the sludge through a series of
rollers apply increasing pressure and shear force on the sludge.
The chamber pressure filters consist of a collection of cloth covered
plates arranged in parallel and pressed together by pressures up to 200
psi. As the plates are compressed, filtrate exits through the cloth.
Gravity-fed or pressurized granular media filter systems are less energy
intensive than the three systems mentioned but require highly qualified
operators with sufficient experience in backflushing operations. These
systems are not applicable toward the removal of dissolved chemical
species.
Waste Type Handled
Pressurized and gravity-fed granular media filtration systems are used for
waste streams containing suspended solids.
Vacuum, belt press, and chamber pressure filtration processes are primarily
used to dewater sludge.
Restrictive Waste Characteristics
Energy intensive filtration operations such as belt press filtration,
vacuum rotary filtration and pressure filters operate at an optimal percent
solids content. Sludges which range from five to ten percent solids are
ideally suited for vacuum, belt press, and chamber pressure filtration
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processes. Sludges with less solids content may require a pretreatment
operation that will increase the solids concentration to this operational
range. Pressurized and gravity-feed media filtration processes are most
effective on suspended solids in the range of 100 to 200 mg/L or less. If
the influent waste cannot meet these requirements, then additional
prefiltration operations are required. Belt press filtration systems
require larger amounts of conditioning chemicals than the other options.
Environmental Impacts
Filtration is not a destructive process and therefore produces a highly
concentrated dewatered sludge that may be quite toxic. Sludge
management/disposal is addressed in Section 5.1.
Costs
Costs for a portable gravity or a pressurized granular media filtering
apparatus are not available. However, typical costs for constructed
filters used in stationary water treatment facilities are available. A
plant capable of handling I MGD requires an annual operation and
maintenance budget of approximately $590,000 in 1985 dollars. The capital
costs for construction of the plant would be approximately $95,400 in 1985
dollars (Jacobs Engineering, 1986).
Annual estimated O&M costs for a portable filter press used for dewatering
20,000 gals per year with a 2 percent solids content are $13,000 per year.
Capital costs for the same system are estimated at approximately $20,800
(Jacobs Engineering, 1986).
Commercial Applications
Tetra Recovery Systems has two mobile filtration units, a filter press and
a sludge dewatering unit. Both units produce two cubic yards of dry sludge
per hour.
Industrial Innovations, Inc. has a mobile vacuum filtration unit. The unit
is capable of handling 100-200 gpm.
Other companies producing mobile filtration units are Carbon Air Services,
Inc., Mobile Solvent Declaimers, Inc., and National Dredging and Plumbing
Corp.
A number of vendors use filtration as part of a total treatment system.
These vendors are Chemical Waste Management, Inc., Enviro-Chem Waste
Management Service, and Rexnord, Inc. These units vary in size from
1,000-10,000 gpd.
Vendor addresses and contacts are presented in the appendix.
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5.10 ION EXCHANGE
Process Description
Anions and cations dissolved in a dilute aqueous waste can be removed from
solution through the process of ion exchange. As the name implies, one
ion, electrostatically attached to a solid resin material, is exchanged for
a dissolved toxic ion. The exchange reaction is reversible, which allows
for resin regeneration.
The exchange occurs because the divalent and and trivalent toxic metal
anions or cations have an increased affinity for the charged sites on the
surface of the resins. These resins are originally coated with weakly held
monovalent anions or cations such as chloride, hydroxyl, sodium or hydrogen
ions.
Currently, the majority of new ion exchange resins are constructed of
synthetic organic materials. The new resins are able to withstand a wide
range of temperatures and pH and are capable of specific selectivity if
ions have a high exchange capacity.
It is possible to remove both dissolved toxic anions and cations by placing
a cation exchange column and anion exchange column in series. This system
has the capability, depending upon the choice of resins, to remove a wide
range of inorganic and organic dissolved contaminants.
Small, trailer-mounted ion exchange systems have been in operation since
1977. The typical range of pressure vessels are from two-to six-inch
diameter systems up to a custom size of 12 feet in diameter. Corresponding
flow rates range from 25 gpm up to a maximum of 1150 gpm. These vessels
could easily be truck-mounted and moved from site to site.
Waste Types Handled
Wastes that are suited for anion exchange include:
o All metallic anions and cations such as
Cr20? , Se04 , As04 , Ni , Cd , or Hg ,
o Inorganic anions such as halides, sulfates and cyanides,
o Organic acids such as carboxylics, sulfonics and some phenols, and
o Organic bases such as amines.
Restrictive Waste Characteristics
The upper limits of concentration to which ion exchange may be applied are
2,500 mg/1 for dissolved ions and 50 mg/1 for suspended solids. Higher
concentration levels of dissolved ion will result in rapid exhaustion of
the resin with unusually high regeneration expenses. High concentrations
of suspended solids will result in clogged columns. Oxidants in the waste
stream should also be avoided.
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Required Onsite Facilities/Capabilities
Ion exchange units can be skid-mounted and placed on a flat bed truck or a
railcar for transport to various sites.
Additional equipment required includes:
o Pumps and piping,
o Backwash equipment, and
o A regeneration system.
Property graded access roads and staging areas will be required.
Environmental Impacts
During resin regeneration, a concentrated toxic backwash stream is
produced. As a result, an ion exchange system must be capable of handling
this waste stream. Depending upon the waste characteristics, additional
treatment of this stream, via such processes as precipitation and
neutralization, will be required as discussed in Section 5.1.
Although exchange columns can be operated manually or automatically, manual
operation is better suited for hazardous waste site applications because of
the diversity of wastes encountered. Manual operation requires a skilled
operator familiar with the process.
Costs
The costs of small mobile ion exchange systems are not available. However,
an ion exchange system servicing a flow of 50 gpm required an initial
capital investment of $84,000 and an annual operation and maintenance cost
of $14,500.
These cost estimates were initially in 1979 dollars; they were escalated to
1986 dollars using the Marshall and Swift Index. The cost for a smaller
mobile system should be less.
Commercial Applications
Since 1977, Eco-Tec Limited has marketed a skid-mounted acid waste
purification and recovery system. They report a 50 percent (by weight)
recovery of nitric acid from a nickel-stripping process. Recently Carbon
Air Services, Inc., Holtz Bio Engineering and Westinghouse Waste Technology
Services Division have introduced mobile ion exchange units. Also a large
number of companies market fixed ion exchange systems such as Eastman
Kodak, Pennwalt Corp., VOP Inc. and Darcel Chemical Industries, but do not
market a mobile system at this time.
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5.11 MEMBRANE SEPARATION
Process Description
Membrane technologies separate solutes or contaminants from liquids through
the use of semi-permeable membranes. Semi-permeable membranes function by
selectively rejecting contaminants based on pore size, ion valence or
co-precipitation. Membrane separation processes can be used for volume
reduction, purification, concentration, and/or recovery of the
contaminants.
The types of membrane separation technologies include reverse osmosis,
hyperfiltration, ultrafiltration and electrodialysis. At the present time,
reverse osmosis (RO) is the only technology that has been used as a mobile
system and thus will be the only one considered in this section.
The RO system allows a solvent (such as water) to be removed from a
solution containing solutes (such as salts) by the application of a
pressure driven membrane process. In this process, the solvent molecules
(water) are forced through the microscopic pores of a semi-permeable
membrane by achieving sufficient hydrostatic pressure to overcome the
concentrate osmotic pressure. Operating pressures for a typical reverse
osmosis system can range from 200 to 800 psi. As the solvent flows through
the membrane, the larger organic and inorganic compounds are rejected.
The effectiveness of systems RO depends on the following factors:
o Temperature of the solution,
o Pressure of the system,
o pH of the solution, and
o Chemical and physical structure of the membrane.
Waste Types Handled
The RO process has typically been used for treatment of brackish waters and
aqueous metal wastes (plating baths), but innovative technologies have
made it very effective in treating other forms of contaminants such as the
following:
o PCB and chlorinated organics in groundwater,
o Waters with high BOD levels present,
o Insecticides/herbicides in groundwater, and
o Organic and inorganic leachate.
Concentration levels of organics generally range in the milligram per liter
level for the feed with a permeate in the range of 10-50 micrograms per
liter.
Restrictive Waste Characteristics
To avoid membrane plugging and to insure a long maintenance life, it is
important to remove suspended solids and oils with conventional
pretreatment. The application of RO to a hazardous waste stream must be
carefully evaluated on a pilot or bench-scale basis, because of the
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potential for the chemicals to react with the membranes leading to
deterioration or destruction.
Environmental Impacts
Process residuals include:
o Solutes that remain in the effluent in the range of 10-100 ug/L, and
o Concentrate solution (10-20 percent of feed volume).
Further treatment would include dewatering/evaporation followed by fixation
of the sludges.
Costs
Capital costs for a mobile RO system can range from $40,000 for a 10 gpm
facility to $200,000 for a 100 gpm facility (Environmental Canada, 1986).
Operating and maintenance costs can range from $20,000/year for a 10 gpm
facility to $100,000/year for a 100 gpm facility.
Commercial Applications
A mobile self-contained RO unit was built by Memtek Corp. of Nepean,
Ontario for the Environmental Protection Service (EPS) branch of
Environmental Canada.
The EPS mobile reverse osmosis unit is a completely self-contained
trailer-mounted unit that is transportable by helicopter.
This unit was used at a variety of sites throughout Canada, including:
o Gloucester Landfill,
o An unspecified site in Western Canada, and
o A wood preserving site in Alberta Province.
Leachate from the Gloucester Landfill underwent a 30-day trial run. Dilute
organic solutions were concentrated at an average removal of 77% from the
permeate, with the permeate/concentrate ratio of 10:1. A removal of 88%
was achieved at a permeate/concentrate ratio of 6:1. The organic compounds
that were successfully removed include:
o Acetone,
o 1,2-dichloroethane,
o 1,1-dichloroethane/THF1,
o Trichloroethane,
o Chloroform,
o 1,1,1-Trichloroethane,
o Diethyl ether, and
o Benzene.
This RO system has also removed PCBs from groundwater at a feed
concentration of 15 ug/L. Insecticides/pesticides from an industrial spill
site were removed from groundwater with up to 99.9 percent removal.
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5.12 PHASE SEPARATION
Process Description
Phase separation is used for separating solid/liquid or liquid/liquid
suspensions with different specific gravities. It encompasses many
different processes. Several of the processes that may be used for
separation are described below.
o Oil separation - this process employs a number of equipment
configurations to remove oil from water. Each provides surface
contact for de-emulsifying the oil particles from the water phase.
A coalescer is a flow-through chamber with metal sheets inclined at
a 45 angle in the middle. The metal surface enables small oil
droplets to agglomerate together to form a continuous oil phase.
The lighter oil fraction then travels to the top of the chamber
where it is skimmed off the top.
o Centrification - in this process, the components of the oil/liquid
mixture are separated mechanically by application of centrifugal
force. Centrifugal forces are applied by rapidly rotating the
mixture in a confined vessel. The suspended oils will migrate
towards the center of the vessel. Centrifuges may also be used for
the separation of liquid/solid mixtures.
o Dissolved air flotation (DAF) - these processes are also used to
separate emulsified oils from water by first dissolving air (under
high pressure) into the water and then dropping the pressure. Tiny
air bubbles are generated throughout the water phase. The oils
accumulate at the air-water interface and are carried to the top of
the chamber where they are skimmed off. DAF units are usually
employed for more complete oil removal, whereas coalescers are used
for coarse oil separation. A schematic diagram of a DAF system is
given in Figure 5.7.
Key operating parameters for mobile phase separation units are listed below:
o Oil concentration,
o Detention time,
o Surface area,
o Skimming rate,
o Air pressure,
o RPM, and
o Treatment chemical needed.
Waste Type Handled
The following is a list of wastes that can be treated with phase
separation:
o Immissible oily liquids in water,
o Suspended solids,
o Hydrophobic chemicals, and
o Two phase leachates.
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Air/Solids Mix-\ QO
Recycle J/rf
C71
I
00
Source: Peabody-Welles, Roscoe, IL
Pressurized
Bubbles
Liquid
Light
Solids
Heavy
Solids
(Sludge)
FIGURE 5.7
SCHEMATIC DIAGRAM OF RECYCLE FLOW DISSOLVED AIR FLOTATION SYSTEM
-------
Restrictive Waste Characteristics
Dissolved organic or inorganic contaminants will not be removed by this
process.
Required Onsite Facilities/Capabilities
Mobile phase separation units are available and can be used at most sites,
provided that electrical and water supply are available. The systems are
simple in configuration and easy to operate under field conditions.
Environmental Impacts
The oil layer which is separated by this process can be recycled for the
following uses:
o Reused solvent,
o Auxiliary fuel, and
o Distilled products.
Disposal of residuals is discussed in Section 5.1.
Costs
The costs for mobile phase separation processes are not available.
However, the costs for a small fixed-air flotation unit and small
centrification unit are available. The costs for a fixed-air flotation
unit with a 100,000 gpd throughput are $190,000 for capital costs and
$64,000 for an annual O&M. The costs for a fixed centrification unit with
a throughput capacity of 50 IbsXhour(dry) are $500,000 for capital cost and
$84,000 for an annual O&M (Jacobs Engineering, 1986).
Commercial Applications
The following is a partial list of mobile phase separator suppliers:
o Bird Environmental Systems,
o IT Corp.,
o Tetra Recovery System,
o Industrial Innovations, Inc.,
o Enviro-Chem Waste Management Services, Inc. and
o National Dredging and Pumping Corp.
Addresses and contacts are presented in the appendix.
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6.0 BIOLOGICAL TREATMENT
6.1 INTRODUCTION
Several well-developed biological technologies exist for the treatment of
aqueous waste streams contaminated at low to'moderate levels with
non-halogenated organics and some halogenated organics. Addition of
powdered activated carbon significantly improves treatment performance and
permits removal of non-biodegradable organics such as pesticides or
herbicides. In addition, enhanced in situ biodegradation is being
developed for sites having soil and groundwater contaminated with readily
biodegradable organics.
The basic processes available are:
o Aerobic biological treatment - tank-based processes using oxygen
metabolizing microorganisms and careful process control for
low-strength aqueous waste streams.
o Anaerobic biological treatment - tank-based processes using
microorganisms capable of chemical biodegradation in the absence
of oxygen. Careful process control and extended retention time
required.
o In situ biodegradation - use of existing indigenous aerobic
bacteria or introduced cultured strains in soil. Activity is often
accelerated with addition of nutrients. Biodegradation of organics
in soil or groundwater may require from 6 to 18 months.
Aerobic and anaerobic tank-based processes will generate residual biomass
sludge which will require further treatment and disposal. Vendors of
mobile biological units can design and/or provide systems for treatment and
disposal, which may utilize thermal, physical, chemical or immobilization
processes.
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6.2 AEROBIC BIOLOGICAL TREATMENT
Process Description
Aerobic biological treatment consists or conventional activated sludge
processes as well as modifications of these processes including:
o Sequential batch reactors,
o Rotating biological contactors,
o Trickling filters, and
o Fixed film reactors.
All of these systems can treat aqueous waste streams contaminated with low
levels of non-halogenated organics and/or certain halogenated organics.
Addition of powdered activated carbon can significantly improve treatment
of halogenated organics. Readily available mobile units include:
o Compact fixed film reactors,
o Fluidized bed reactors, and
o Membrane reactors utilizing filtration and biomass recycling.
Figure 6.1 illustrates a conventional activated sludge process and Figure
6.2 shows a rotating biological contactor.
Waste Types Handled
Mobile, tank-based aerobic reactors can handle many non-halogenated
organics according to several vendors of this process (Superfund Treatment
Technologies: A Vendor Inventory, EPA, 1986). Efficient operation may
require use of specially cultured bacterial strains. A few of the organics
that may be handled by this sytem are listed below*:
Concentration Removal Efficiency
o Phenols up to 350 mg/L 99%
o Formaldehyde up to 300 mg/L 99%
o #2 Fuel Oil up to 300 mg/L 98%
o PCP up to 20 mg/L 90%
Low levels of heavy metals are often removed through adsorption to the
biomass.
*Polybac Corporation, Superfund Treatment Technologies; A Vendor
Inventory, EPA, 1986.
6-2
-------
en
i
OJ
Aeration
Stage
i
Wastewater | [ * ' n "~^
Feed-*^ 1 \'/
e
' * *
. . *
.. ' » ° ' '
f\ i r ^HM^^to o Y ? 0 v A ^ ^ j
1 L>«_
~ Air Bubbles
J^ J
Fixed Air
;jr Bubble
,, r
Assembly
B
Clarifier
Stage
|
^5jjt£
k«
1
Illlllll
L_
^
Activated Sludge Recycle
Effluent
FIGURE 6.1
SCHEMATIC DIAGRAM OF ACTIVATED SLUDGE BIOLOGICAL TREATMENT
-------
CH,,end
INFLUENT WASTEWATER
WITH ORGANIC MATERIAL
EFFLUENT WASTEWATER
WITH OXIDIZED ORGANICS
ROTATING BIOLOGICAL CONTACTOR
(COURTESY OF ENVIREXl
FIGURE 6.2
SCHEMATIC DIAGRAM OF ROTATING BIOLOGICAL CONTACTOR
-------
Addition of powdered activated carbon may permit treatment of aqueous waste
streams contaminated at low to moderate levels with:
o Pesticides and herbicides,
o Halogenated hydrocarbons, and
o Halogenated solvents.
Restrictive Waste Characteristics
Biological reactors require stable operating conditions. Abrupt changes in
waste stream characteristics can generate shock loading to the biomass.
The maintenance of stable levels is crucial for a number of key
environmental parameters in the waste stream, including:
o Dissolved oxygen (1 to 3 mg/L minimum),
o pH (6 to 8),
o Nutrients (phosphorous, nitrogen, carbon),
o Alkalinity (provides buffering capacity),
o Minimal levels of suspended solids (particularly for fixed film
reactors), and
o Liquid retention times of 2 to 5 hours.
Mobile biological reactors can be used for groundwater treatment due to the
relative stability of groundwater characteristics.
The biomass is susceptible to elevated levels of heavy metals or
halogenated organics. These may be overcome with the addition of the
following:
o Powdered or granular activated carbon, or
o Pretreatment using physical/chemical treatment units to remove
problematic waste types.
Pilot studies are necessary to determine process feasibility on specific
wastes.
Required Onsite Facilities/Capabilities
Mobile biological reactors are relatively simple systems and are readily
transportable. Specific requirements include:
o Pumps for circulation and aeration (hence electric power is
required), and
6-5
-------
o Careful monitoring of the biodegradation process and water quality
parameters for more concentrated waste streams, often requiring an
onsite lab facility.
Environmental Impacts
Settled sludge and/or excess biomass residues may contain elevated levels
of organics or heavy metals. Sludge will require dewatering and may be
shipped off site for disposal at a treatment and disposal facility.
Use of activated carbon for removal of halogenated organics will produce a
mixture of spent carbon and biomass sludge as residuals. Treatment can
include:
o Dewatering and removal off site, or
o Carbon regeneration and sludge destruction using wet air oxidation.
Generation of undesirable odors or the driving off of volatile organic
compounds from the aeration tasks may necessitate the use of special
venting and filtering procedures for gases.
Costs
While costs vary according to the site, some cost ranges have been
estimated by vendors for hazardous waste site scenarios (Superfund
Treatment Technologies: A Vendor Inventory, EPA, 1986).
Cost
High Strength Leachate
2,000 gpd $0.25 to 0.35/gallon
(high levels of metals and organics)
Contaminated Groundwater
10,000 gpd
Average 40 ppm VOCs $0.05 to 0.09/gallon
Costs for biological treatment can be a small fraction of the cost for
comparable chemical/physical systems. This is due to the simplicity of the
process and the use of self-sustaining microorganisms as the primary
treatment process. More complicated waste streams will require more
expensive multi-step treatment trains.
Commercial Applications
Several companies have developed mobile biological reactors which are well
suited to treatment of aqueous waste streams contaminated at low levels
with organics. They include:
DETOX, Inc.
Dorr-Oliver, Inc.
Polybac Corp.
Zimpro, Inc.
6-6
-------
TABLE 6.1
MGBILE BIOLOGICAL TREATMENT SYSIBG
Dorr-Oliver, Inc.
FMC Aquifer
Remediation
Systems
Polybac Corp.
Zimpro Inc.
Process
Aerobic or anaerobic
biological treatment
with fixed film or
membrane reactor
In situ enhancement
or acceleration of
natural bacterial
biodegradation
Aerobic or anaerobic
fixed film reactor
In situ biodegrada-
tion using cultured
bacterial strains
Aerobic reactor
augmented with
powered activated
carbon treatment
(PACT)
Units
Up to 8 tank
reactors
Capacity Waste Type Handled
Maximum of
10,000 gpd
Little equip-
ment required.
May use
injection system
with groundwater
recirculation
13 tank
reactors
Variable.
May require
groundwater
recirculation
system
1 tank
reactor
Site-
dependent
6,000 to
25,000 gpd
Site-
dependent
18,000 gpd
Aerobic; primarily
nonhalogenated
organics
Anaerobic: some
halogenated organics
at moderate levels
Primarily readily
biodegradable
organics in soil or
groundwater
Most nonhalogenated
organics, some
halogenated organics
Readily biodegrad-
able organics in
soil or groundwater
Nonhalogenated and
halogenated organics,
including pesticides
6-7
-------
Available systems are described in Table 6.1. Addresses and contacts are
listed in the appendix.
6-8
-------
6.3 ANAEROBIC DIGESTION
Process Description
Anaerobic digestion is a biodegradation process capable of handling high
strength aqueous waste streams that would not be efficiently treated by
aerobic biodegradation processes. Advantages of anaerobic systems over
aerobic systems include:
o Capability to break down some halogenated organics,
o Low production of biomass sludges that require further treatment and
disposal, and
o Low cost.
However, anaerobic systems can be less reliable than aerobic systems. For
this reason, aerobic systems are better suited for mobile unit
applications. Disadvantages of anaerobic systems include:
o Potential for shock loading of biomass and termination of
biodegradation process due to variation in waste stream
characteristics,
o Low throughput due to the slow biodegradation process (two steps),
o Frequent necessity for further treatment of effluent prior to
discharge offsite or to a municipal treatment system, and
o Generation of methane gas (a problem if it cannot be readily used
on site for meeting energy requirements).
Careful design and control can often solve these problems, but vendors are
reluctant to recommend anaerobic mobile systems. Anaerobic systems are
more susceptible to variation in waste stream characteristics and
environmental parameters. Fixed anaerobic systems are widely used in
industry for treatment of uniform, concentrated biodegradable waste in
aqueous waste streams due to the low cost, low residual generation and
production of usable methane gas. However, application to variable CERCLA
waste streams is relatively infrequent. Anaerobic systems have the best
potential as pretreatment step for an aerobic system that would otherwise
be unable to process a high strength waste such as a leachate.
Figure 6.3 is a process diagram for an anaerobic system.
Waste Types Handled
Anaerobic digesters can handle concentrated waste streams with
biodegradable nonhalogenated organics and moderate levels of halogenated
organics. The most suitable application may be as a treatment step for
landfill leachates where storage, mixing and flow regulation can be
accomplished prior to introduction to the digestors.
6-9
-------
GAS WITHDRAWAL
.GAS WITHDRAWAL
GAS
INLET
01
i
JSZ1
/ / / SCUM LAYER / / /
SUPERNATANT
ACTIVE LAYER
\ \ > \ \
STABILIZED
SOLIDS
\
SOLIDS
REMOVAL
CONVENTIONAL
IE OUTLET
INLET
GAS
OUTLET
HIGH RATE
FIGURE 6.3
SCHEMATIC DIAGRAM OF CONVENTIONAL AND HIGH RATE ANAEROBIC DIGESTERS
-------
Anaerobic digestion can partially break down some halogenated organics
unsuitable for aerobic digestion. Anaerobic systems can also be used as a
pretreatment step prior to aerobic biodegradation. Recommended influent
characteristics for anaerobic processes are listed below:
o BOD 1000 to 15,000 mg/1
o COD >1500 mg/L
Restrictive Waste Characteristics
As with aerobic systems, the biodegradation process can be slowed or halted
by the following:
o Abrupt change in waste stream characteristics,
o Variable environmental conditions (e.g., temperature, pH),
o Elevated levels of heavy metals or halogenated organics toxic to the
biomass, and
o Inadequate nutrient levels.
Required Onsite Facilities/Capabilities
Onsite system use requires the following:
o Consideration of the volume to be treated (flow through anaerobic
systems is low and retention times range from 1 to 5 days or more,
depending on the waste stream),
o Pilot studies to determine feasibility, and
o Careful monitoring of digester operating parameters, which requires
an onsite or nearby offsite lab facility.
Environmental Impacts
Operation of a digester on site will generate some minor impacts, which are
outlined below.
o Methane gas is produced and must be utilized or disposed of,
o Additional treatment of effluent from the digestor will be required,
o Undesirable odors may be generated, and
o Disposal of residuals will be required (volume is considerably less
than that produced by aerobic systems).
Costs
Costs are similar to those quoted for aerobic systems.
6-11
-------
Commercial Applications
Most of the companies that offer mobile aerobic biological systems also
offer anaerobic systems. The companies are listed below. See Table 6.1
for system details. Contacts and addresses are listed in the appendix.
Polybac Corp.
Dorr-Oliver, Inc.
DETOX, Inc.
6-12
-------
6.4 IN SITU BIODEGRADATION
Process Description
In situ biodegradation is a process that uses existing indigenous aerobic
bacteria, or introduced cultured strains of bacteria, to biodegrade organic
compounds in soil or groundwater. Since the'biodegradation process occurs
below water or ground surface, precise process control is not feasible.
However, the biological process may be accelerated by introducing
supplemental materials, including:
o Nutrients (phosphorous, nitrogen),
o Oxygen, and
o Cultured bacterial strains.
In situ biodgradation is often used in conjunction with a groundwater
pumping and reinjection system to circulate nutrients and oxygen through a
contaminated aquifer and associated soils. It can provide substantial
reduction in contaminant levels in soils and groundwater at a fraction of
the cost of soil excavation and/or above-ground pump and treat systems.
Such a system is depicted on Figure 6.4.
Waste Types Handled
To date, in situ biodegradation has been applied to sites contaminated with
readily biodegradable nonhalogenated organics, primarily gasoline.
Applications can include the following waste types:
o Gasoline and fuel oils,
o Hydrocarbon solvents (e.g., benzene, toluene, xylene),
o Nonhalogenated aromatics (e.g., ethylbenzene, stryene, phenol,
cresol), and
o Alcohols, ketones, ethers and glycol.
The most common applications have been at gasoline spill sites where
conventional excavation and/or treatment methods are very costly.
Before in situ biodegradation can be used, wastes must be evaluated for:
o Biodegradability,
o Oxygen requirement,
o Nutrient requirement for biodegradation,
o Solubility,
6-13
-------
01
i>
-£>
RECYCLED
GROUND
WATER
Undegraded
Contaminant
Treatment &
Removal
NUTRIENT FLOW
Addition ofl E=3 BIOACTIVE
Nutrient & I r] CONTAMINANT
Oxygen '
NEW WATER
TABLE
ORIGINAL
WATER TABLE
Source: FMC Aquifer Remediation Systems
FIGURE 6.4
SCHEMATIC DIAGRAM OF IN SITU BIODEGRADATION
-------
o Inhibitory effects at various concentrations, and
o Total quantity contained on site.
Waste Restrictive Characteristics
In situ biodegradation is generally inhibited by:
o Halogenated organics,
o Elevated levels of metals, and
o Elevated levels of inorganics such as chlorides, acids, or caustics.
Site Requirements
A number of site-specific factors are critical in evaluating the potential
for use of in situ biodegradation on that site. These include:
o Site geology,
o Soil characteristics, including
- permeability
- pH
- moisture content
- organic content
o Aquifer characteristics and hydrogeology,
o Water quality parameters, including
- dissolved oxygen
- pH
- alkalinity
- available nutrients
o Subsurface temperatures.
In general, suitable sites would meet the following criteria:
o Site geology and hydrology allowing for ready pumping and extraction
of contaminated water, followed by reinjection and recirculation,
o Soils with neutral pH, high permeability and moisture content of 50
to 75 percent, and
o Water quality parameters in ranges such that inhibition of
biological activity does not occur.
Required Onsite Facilities/Capabilities
Following positive evaluation of site environmental factors and waste
characteristics, systems for introduction of nutrients and oxygen into
6-15
-------
groundwater and soil must be developed. These may include pumping and
recirculation or infiltration galleries.
Soil and water quality characteristics must be monitored at regular
intervals, and nutrient/oxygen supplies adjusted. Biodegradation may
continue for several months, and final results may not be apparent for one
to two years. Contaminant levels in soil and water may or may not drop
below designated action levels.
Environmental Impacts
The long-term effects of nutrient introduction on groundwater must be
evaluated. Another environmental concern is that the final contaminant
reduction is generally not predictable. In spite of these concerns,
in situ biodegradation is a simple process, requiring minimal site
preparation and producing less site disruption.
Costs
In situ biodegradation may produce acceptable results at costs far below
conventional treatment systems.
While costs are difficult to generalize, examples cited by vendors
suggested costs could be as low as 10 percent of excavation and/or pump and
treat costs. The potential for use in remediation of subsurface gasoline
tank leaks merits serious consideration.
Commercial Applications
Several firms listed in the Table 6-1 and below offer complete in situ
biodegradation systems and services.
Bio Systems, Inc.
FMC-Aquifer Remediation Systems
Geraghty and Miller
O.H. Materials
Polybac Corp.
6-16
-------
REFERENCES
1. Berger, B.B., et al., Control of Organic Substances in Water and
Wastewater, EPA-600/8-33-011, April 1983.
2. Edwards, B.H., et al., Noyes Data Corporation. Emerging Technologies
for the Control of Hazardous Wastes, p.'76-87, 105-108, 119-122, 1983.
3. EPA, Superfund Treatment Technologies: A Vendor Inventory, Prepared
by Camp Dresser & McKee Inc. for the Office of Solid Waste and
Emergency Response, EPA Contract Number 68-01-0753, Linda Galer,
Project Officer, September 1986.
4. Pagan, Robert E., et al., "Kinetics of the Acid Hydrolysis of
Cellulose Found in Paper Refuse," Engineering Science and Technology,
Vol. 5, No. 6, p. 545-547, June 1971.
5. Galze, W.H., et al., Final Report, EPA Grant No. R-804640, U.S.
Environmental Protection Agency, Municipal Environmental Research
Laboratory, Cincinnati, OH, J.K. Carswell, Project Officer.
6. IT Corporation, Transportable Incineration Systems, U.S. Environmental
Protection Agency, Contract No. 68-03-3069, Edison, New Jersey,
February 1984.
7. Jacobs Engineering, Cost Estimates for the Siting, Permitting and
Construction of New Hazardous Waste Treatment Facilities, EPA OSW
Waste Treatment Branch, February 1986.
8. Kirk, Raymond E., and Othmer, Donald F., Encyclopedia of Chemical
Technology, Volume 5, Anthony Stancen, Executive Editor, 1964, p. 132.
9. L. Kotoszka, Nepera Chemical Co., and J. Flood, EPA, "Process
Technology: A Guide to EPA - Approved PCB Disposal Methods," July 8,
1985, p. 41-43.
10. Metcalf and Eddy, Inc., Wastewater Engineering Treatment Disp. Sal.,
McGraw Hill Book Company, 1979.
11. Noyes Data Corporation, "Unit Operations for Treatment of Hazardous
Industrial Wastes", Pollution Technology Review No. 47, Park Ridge,
New Jersey, 1978, p. 621.
12. Ibid, p. 552.
13. Office of Technology Assessment, Technologies and Management
Strategies for Hazardous Waste Control, Washington, D.C., p. 155,
1985.
14. Olexsey, Robert, "Hazardous Waste Management: Treatment Technologies
for Hazardous Wastes," Journal of the Air Pollution Association, 1986,
p. 66-76.
-------
15. The Proctor & Redfern Group, Generic Process Technologies Study,
Toronto, Ontario, July 20, 1982.
16. Prengle, H.W., et al., "Ozone/UV Oxidation of Chlorinated Compounds in
Water," presented at 101 Forum on Ozone Disinfection, Chicago, IL,
June 2-4, 1976.
17. Versar, Inc., Nev Emerging Alternative Technologies, Springfield, VA,
July 17, 1985.
18. Versar, Inc., Assessment of Thermal Treatment Technologies for
Hazardous Waste and Their Restrictive Waste Characteristics, Volume
ID, Springfield, VA, August 30, 1985.
-------
APPENDIX A
LIST OF FIRMS BY TREATMENT PROCESS TECHNOLOGY
Biological
DETOX, Inc.
P.O. Box 324
Dayton, OH 45458
513-433-7394
(Evan Nyer)
Dorr-Oliver
77 Havemeyer Lane
P.O. Box 9312
Stamford, CT 06904
203-358-3664
(Dr. Paul Sutton)
FMC Aquifer Remediation Systems
P.O. Box 8
Princeton, NJ 08540
609-452-2300
(Joan Ridler)
Groundwater Decontamination Systems
140 Route 17, North Suite 210
Paramus, NJ 07652
201-265-6727
OH Materials
P.O. Box 551
Findley, OH 45839
419-423-3526
Polybac Corporation
954 Marcon Blvd.
Allentown, PA 18103
215-264-8740
(William Ronyack and Curtis McDowell)
Zimpro Inc.
Military Road
Rothchild, VI 54474
715-359-7211
(J. Robert Nicholson)
A-l
-------
Physical/Chemical
Accurex
Cincinnati, OH
415-964-3200
(Jim Thompson)
American Toxic Disposal, Inc.
560 Seahorse Drive
Waukegan, IL 60085
312-336-6067
(William Meenan)
Andco Environmental Processes, Inc.
595 Commerce Drive
Amherst, NY 14150
716-691-2100
(Joseph Duffey)
ATW - Calweld Inc.
11300 South Norwalk Blvd.
Santa Fe Springs, CA 90670
213-929-8103
(John Royle)
Bird Environmental Systems
100 Neponset Street
South Walpole, MA 01071
(Neil D. Policow)
Calgon Carbon Corporation
P.O. Box 717
Pittsburgh, PA 15230
412-787-6700
(Joseph Rizzo)
Carbon Air Services
P.O. Box 5117
Hopkins, MN 55343
612-935-1844
(Bruce Anderson)
Chemical Processors, Inc.
5501 Airport Way - So.
Seattle, WA 98108
206-767-0350
(Ron West)
Chemical Waste Management
150 West 137th Street
Riverdale, IL 60627
312-841-8360
(Peter Daley)
A-2
-------
Critical Fluid Systems
25 Acorn Park
Cambridge, MA 02140
617-492-1631
(Peter Dunlap)
DETOX, Inc.
Dayton, OH 45459
513-433-7394
(Evan Nyer)
Ecolochem, Inc.
4545 Patent Rd.
P.O. Box 12775
Norfolk, VA 23502
800-446-8004
(Richard Smallwood)
EPA/Releases Control Branch
Woodbridge Avenue
Edison, NJ 08837
201-321-6677
(Richard Travers)
Ensotech, Inc.
11550 Vanowen St.
North Hollywood, CA 91605
818-982-4895
(Doug Smith)
Envirochem Waste Management Services
P.O. Box 10784
Raleigh, NC 27605
919-469-8490
(Jerry Deakle)
Industrial Innovations, Inc.
P.O. Box 830
Stockton, CA 95201
209-462-8241
(Alfred Abila)
IT Corporation
4575 Pacheco Blvd.
Martinez, CA 94553
415-228-5100
(Ed Sirota)
Kipin Industries
513 Green Garden Road
Aliquippa, PA 15001
412-495-6200
(Peter Kipin)
A-3
-------
Mobile Solvent Reclaimers
RR 1
St. Joseph., MO 64507
816-232-3972
(Larry Lambing)
Newpark Waste Treatment Systems
200A Bourgess Drive
Broussard, LA 70518
713-963-9107
OH Materials
Nationwide
419-423-3526
(Joe Kirk)
Oil Recovery Systems, Inc.
Nationwide
617-769-7600
PPM Inc.
10 Central Avenue
Kansas City, MO 66118
913-621-4206
(Fred Labser)
Resource Conservation Co.
3630 Cornus Lane
Ellicott City, MD 21043
(Lenny Weimer)
Rexnord C.R.I.C.
5103 West Beloit Road
Milwaukee, WI 53201
414-643-2762
(Richard Osantowski)
Richard Sanitary Services
205 41st Street
Richmond, CA 94802
415-236-8000
(Caesar Nuti)
Roy F. Weston, Inc.
Weston Way
West Chester, PA 19380
215-692-3030
(John W. Noland, Nancy P. McDevitt)
Solidtek
5371 Cook Road
Morrow, GA 30260
404-361-6181
(Ed Shuster)
A-4
-------
Sunohio
1700 Gateway Blvd., S.E.
Canton, OH 44707
216-452-0837
(Doug Toman)
Terra Vac, Inc.
356 Fortaleza Street
San Juan, PR 00901
809-723-9171
(Jim Malot)
Tetra Recovery Systems
1121 Boyce Road, Suite 1300
Pittsburgh, PA 15241
412-777-5235
(Ogden Clemens)
U.S. Army Toxic and Hazardous Materials Agency
Aberdeen Proving Ground, MD 21005
301-671-2054
A-5
-------
Solidification
Bethlehem Steel
Bldg. H-Room A110
Bethlehem, PA 18016
215-694-2424
(Robert M. McMullan)
Chemfix Inc.
1675 Airline Highway
P.O. Box 1572
Kenner, LA 70063
504-467-2800
(Robert A. Phelan)
Chemical Waste Management
Riverdale Center
150 W. 137th Street
Riverdale, IL 60627
312-841-8360
(Peter Daley)
Envirite Field Services
600 Germantown Pike
Plymouth Meeting, PA 19462
215-825-8877
(Bill Howard)
Envirochem Waste Management
975 Walnut Street
Gary, NC 27511
919-469-8490
(Jerry Deakle)
Hazcon Inc.
P.O. Box 947
Katy, TX 77492
713-391-1085
(Roy Funderburk)
Lopat Enterprises Inc.
1750 Bloomsbury Avenue
Wanamassa, NJ 08812
201-922-6600
(Lewis Flax)
Solidtek Systems Inc.
5371 Cook Road
Morrow, GA 30260
404-361-6181
(Ed Shuster)
A-6
-------
Velsicol Chemical Corporation
2603 Corporate Avenue - Suite 100
Memphis, TN 38132
901-345-1788
(Charles Hanson)
Westinghouse Hittman Nuclear
9151 Runsey Road
Columbia, MD 21045
301-964-5043
(Robert Conner)
Westinghouse Waste Technology Services Division
P.O. Box 286
Madison, PA 15663
412-722-5600
A-7
-------
Thermal
DETOXCO
2700 Ygnacio Valley Road
Walnut Creek, CA
415-930-7997
(Robert McMahon)
ENSCO Environmental Services
Third Floor, First Tennessee Bank Building
Franklin, TN
615-794-1351
(Robert McCormack)
GA Technologies Inc.
P.O. Box 85608
San Diego, CA 92138
619-455-3000
(Harold Diot)
Haztech
5280 Panola Industrial Boulevard
Decature, GA 30035
404-981-9332
(Saul Furstein)
J.M. Huber Corporation
P.O. Box 2831
Borger, TX 79008
806-274-6331
(Jimmy W. Boyd)
John Zink Services
4401 S. Peoria Avenue
P.O. Box 702220
Tulsa, OK
918-747-1371
(Kenneth E. Hastings')
MAECORP Inc.
17450 South Halsted Street
Homewood, IL 60430
312-957-7600
(Hank Mandosa)
Modar Inc.
320 Wilcrest Street, Suite 220
Houston, TX 77042
713-785-5615
(Fred Sieber)
A-8
-------
OH Materials
P.O. Box 551
Findley, OH 45839
419-423-3526
(Sam Insallaco)
Rollins Environmental Services
1 Rollins Plaza
Wilmington, DE 19899
302-479-2700
(Bill Philipbar)
Reidel Environmental Services
P.O. Box 5007
Portland, OR 97205
503-286-4656
(Jack Patterson)
Shirco Infrared Systems Inc.
1195 Empire Central
Dallas, TX 75247-4301
214-630-7511
(George Hay)
Trade Waste Incineration - A Division of
Chemical Waste Management
8000 Maryland, Suite 4400
St. Louis, MO 63105
314-727-5040
(A.J. McCoy)
VerTech Treatment Systems
12000 Pecos Street
Denver, CO 80234
303-452-8800
(Gerald Rappe)
Waste-Tech Services Inc.
445 Union Blvd., Suite 223
Lakewood, CO 80228
303-987-1790
(Elliott Cooper)
Westinghouse Plasma Systems
P.O. Box 350
Madison, PA 15663
412-722-5637
(Bill Mellili)
Winston Technology
6920 N.W. 44th Ct.
Lauderhill, FL 333319
305-748-1769
(Patrick Philips)
A-9
-------
Zimpro Inc.
Military Road
Rothchild, VI 54474
715-359-7211
(J. Robert Nicholson)
A-in
" *U. S. GOVERNMENT PRINTING OFFICE 1986; 621-735/60531
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